[Linux-cachefs] [PATCH 10/14] FS-Cache: Generic filesystem caching facility [try #10]
David Howells
dhowells at redhat.com
Fri May 19 15:47:05 UTC 2006
The attached patch adds a generic intermediary (FS-Cache) by which filesystems
may call on local caching capabilities, and by which local caching backends may
make caches available:
+---------+
| | +--------------+
| NFS |--+ | |
| | | +-->| CacheFS |
+---------+ | +----------+ | | /dev/hda5 |
| | | | +--------------+
+---------+ +-->| | |
| | | |--+
| AFS |----->| FS-Cache |
| | | |--+
+---------+ +-->| | |
| | | | +--------------+
+---------+ | +----------+ | | |
| | | +-->| CacheFiles |
| ISOFS |--+ | /var/cache |
| | +--------------+
+---------+
The patch also documents the netfs interface and the cache backend
interface provided by the facility.
There are a number of reasons why I'm not using i_mapping to do this.
These have been discussed a lot on the LKML and CacheFS mailing lists,
but to summarise the basics:
(1) Most filesystems don't do hole reportage. Holes in files are treated as
blocks of zeros and can't be distinguished otherwise, making it difficult
to distinguish blocks that have been read from the network and cached from
those that haven't.
(2) The backing inode must be fully populated before being exposed to
userspace through the main inode because the VM/VFS goes directly to the
backing inode and does not interrogate the front inode on VM ops.
Therefore:
(a) The backing inode must fit entirely within the cache.
(b) All backed files currently open must fit entirely within the cache at
the same time.
(c) A working set of files in total larger than the cache may not be
cached.
(d) A file may not grow larger than the available space in the cache.
(e) A file that's open and cached, and remotely grows larger than the
cache is potentially stuffed.
(3) Writes go to the backing filesystem, and can only be transferred to the
network when the file is closed.
(4) There's no record of what changes have been made, so the whole file must
be written back.
(5) The pages belong to the backing filesystem, and all metadata associated
with that page are relevant only to the backing filesystem, and not
anything stacked atop it.
The attached patch adds a generic core to which both networking filesystems and
caches may bind. It transfers requests from networking filesystems to
appropriate caches if possible, or else gracefully denies them.
If this facility is disabled in the kernel configuration, then all its
operations will be trivially reducible to nothing by the compiler.
FS-Cache provides the following facilities:
(1) Caches can be added / removed at any time, even whilst in use.
(2) Adds a facility by which tags can be used to refer to caches, even if
they're not mounted yet.
(3) More than one cache can be used at once. Caches can be selected
explicitly by use of tags.
(4) The netfs is provided with an interface that allows either party to
withdraw caching facilities from a file (required for (1)).
(5) A netfs may annotate cache objects that belongs to it.
(6) Cache objects can be pinned and reservations made.
(7) The interface to the netfs returns as few errors as possible, preferring
rather to let the netfs remain oblivious.
(8) Cookies are used to represent indices, files and other objects to the
netfs. The simplest cookie is just a NULL pointer - indicating nothing
cached there.
(9) The netfs is allowed to propose - dynamically - any index hierarchy it
desires, though it must be aware that the index search function is
recursive, stack space is limited, and indices can only be children of
indices.
(10) Indices can be used to group files together to reduce key size and to make
group invalidation easier. The use of indices may make lookup quicker,
but that's cache dependent.
(11) Data I/O is effectively done directly to and from the netfs's pages. The
netfs indicates that page A is at index B of the data-file represented by
cookie C, and that it should be read or written. The cache backend may or
may not start I/O on that page, but if it does, a netfs callback will be
invoked to indicate completion. The I/O may be either synchronous or
asynchronous.
(12) Cookies can be "retired" upon release. At this point FS-Cache will mark
them as obsolete and the index hierarchy rooted at that point will get
recycled.
(13) The netfs provides a "match" function for index searches. In addition to
saying whether a match was made or not, this can also specify that an
entry should be updated or deleted.
FS-Cache maintains a virtual indexing tree in which all indices, files, objects
and pages are kept. Bits of this tree may actually reside in one or more
caches.
FSDEF
|
+------------------------------------+
| |
NFS AFS
| |
+--------------------------+ +-----------+
| | | |
homedir mirror afs.org redhat.com
| | |
+------------+ +---------------+ +----------+
| | | | | |
00001 00002 00007 00125 vol00001 vol00002
| | | | |
+---+---+ +-----+ +---+ +------+------+ +-----+----+
| | | | | | | | | | | | |
PG0 PG1 PG2 PG0 XATTR PG0 PG1 DIRENT DIRENT DIRENT R/W R/O Bak
| |
PG0 +-------+
| |
00001 00003
|
+---+---+
| | |
PG0 PG1 PG2
In the example above, you can see two netfs's being backed: NFS and AFS. These
have different index hierarchies:
(*) The NFS primary index will probably contain per-server indices. Each
server index is indexed by NFS file handles to get data file objects.
Each data file objects can have an array of pages, but may also have
further child objects, such as extended attributes and directory entries.
Extended attribute objects themselves have page-array contents.
(*) The AFS primary index contains per-cell indices. Each cell index contains
per-logical-volume indices. Each of volume index contains up to three
indices for the read-write, read-only and backup mirrors of those volumes.
Each of these contains vnode data file objects, each of which contains an
array of pages.
The very top index is the FS-Cache master index in which individual netfs's
have entries.
Any index object may reside in more than one cache, provided it only has index
children. Any index with non-index object children will be assumed to only
reside in one cache.
The FS-Cache overview can be found in:
Documentation/filesystems/caching/fscache.txt
The netfs API to FS-Cache can be found in:
Documentation/filesystems/caching/netfs-api.txt
The cache backend API to FS-Cache can be found in:
Documentation/filesystems/caching/backend-api.txt
Signed-Off-By: David Howells <dhowells at redhat.com>
---
Documentation/filesystems/caching/backend-api.txt | 345 +++++++
Documentation/filesystems/caching/fscache.txt | 151 +++
Documentation/filesystems/caching/netfs-api.txt | 726 ++++++++++++++
fs/Kconfig | 15
fs/Makefile | 1
fs/fscache/Makefile | 11
fs/fscache/cookie.c | 1063 +++++++++++++++++++++
fs/fscache/fscache-int.h | 93 ++
fs/fscache/fsdef.c | 113 ++
fs/fscache/main.c | 105 ++
fs/fscache/page.c | 548 +++++++++++
include/linux/fscache-cache.h | 226 ++++
include/linux/fscache.h | 486 ++++++++++
13 files changed, 3883 insertions(+), 0 deletions(-)
diff --git a/Documentation/filesystems/caching/backend-api.txt b/Documentation/filesystems/caching/backend-api.txt
new file mode 100644
index 0000000..896c778
--- /dev/null
+++ b/Documentation/filesystems/caching/backend-api.txt
@@ -0,0 +1,345 @@
+ ==========================
+ FS-CACHE CACHE BACKEND API
+ ==========================
+
+The FS-Cache system provides an API by which actual caches can be supplied to
+FS-Cache for it to then serve out to network filesystems and other interested
+parties.
+
+This API is declared in <linux/fscache-cache.h>.
+
+
+====================================
+INITIALISING AND REGISTERING A CACHE
+====================================
+
+To start off, a cache definition must be initialised and registered for each
+cache the backend wants to make available. For instance, CacheFS does this in
+the fill_super() operation on mounting.
+
+The cache definition (struct fscache_cache) should be initialised by calling:
+
+ void fscache_init_cache(struct fscache_cache *cache,
+ struct fscache_cache_ops *ops,
+ const char *idfmt,
+ ...)
+
+Where:
+
+ (*) "cache" is a pointer to the cache definition;
+
+ (*) "ops" is a pointer to the table of operations that the backend supports on
+ this cache;
+
+ (*) and a format and printf-style arguments for constructing a label for the
+ cache.
+
+
+The cache should then be registered with FS-Cache by passing a pointer to the
+previously initialised cache definition to:
+
+ int fscache_add_cache(struct fscache_cache *cache,
+ struct fscache_object *fsdef,
+ const char *tagname);
+
+Two extra arguments should also be supplied:
+
+ (*) "fsdef" which should point to the object representation for the FS-Cache
+ master index in this cache. Netfs primary index entries will be created
+ here.
+
+ (*) "tagname" which, if given, should be a text string naming this cache. If
+ this is NULL, the identifier will be used instead. For CacheFS, the
+ identifier is set to name the underlying block device and the tag can be
+ supplied by mount.
+
+This function may return -ENOMEM if it ran out of memory or -EEXIST if the tag
+is already in use. 0 will be returned on success.
+
+
+=====================
+UNREGISTERING A CACHE
+=====================
+
+A cache can be withdrawn from the system by calling this function with a
+pointer to the cache definition:
+
+ void fscache_withdraw_cache(struct fscache_cache *cache)
+
+In CacheFS's case, this is called by put_super().
+
+
+==================
+FS-CACHE UTILITIES
+==================
+
+FS-Cache provides some utilities that a cache backend may make use of:
+
+ (*) Find the parent of an object:
+
+ struct fscache_object *
+ fscache_find_parent_object(struct fscache_object *object)
+
+ This allows a backend to find the logical parent of an index or data file
+ in the cache hierarchy.
+
+ (*) Note occurrence of an I/O error in a cache:
+
+ void fscache_io_error(struct fscache_cache *cache)
+
+ This tells FS-Cache that an I/O error occurred in the cache. After this
+ has been called, only resource dissociation operations (object and page
+ release) will be passed from the netfs to the cache backend for the
+ specified cache.
+
+ This does not actually withdraw the cache. That must be done separately.
+
+
+========================
+RELEVANT DATA STRUCTURES
+========================
+
+ (*) Index/Data file FS-Cache representation cookie:
+
+ struct fscache_cookie {
+ struct fscache_object_def *def;
+ struct fscache_netfs *netfs;
+ void *netfs_data;
+ ...
+ };
+
+ The fields that might be of use to the backend describe the object
+ definition, the netfs definition and the netfs's data for this cookie.
+ The object definition contain functions supplied by the netfs for loading
+ and matching index entries; these are required to provide some of the
+ cache operations.
+
+ (*) In-cache object representation:
+
+ struct fscache_object {
+ struct fscache_cache *cache;
+ struct fscache_cookie *cookie;
+ unsigned long flags;
+ #define FSCACHE_OBJECT_RECYCLING 1
+ ...
+ };
+
+ Structures of this type should be allocated by the cache backend and
+ passed to FS-Cache when requested by the appropriate cache operation. In
+ the case of CacheFS, they're embedded in CacheFS's internal object
+ structures.
+
+ Each object contains a pointer to the cookie that represents the object it
+ is backing. It also contains a flag that indicates whether the object is
+ being retired when put_object() is called. This should be initialised by
+ calling fscache_object_init(object).
+
+
+================
+CACHE OPERATIONS
+================
+
+The cache backend provides FS-Cache with a table of operations that can be
+performed on the denizens of the cache. These are held in a structure of type:
+
+ struct fscache_cache_ops
+
+ (*) Name of cache provider [mandatory]:
+
+ const char *name
+
+ This isn't strictly an operation, but should be pointed at a string naming
+ the backend.
+
+ (*) Object lookup [mandatory]:
+
+ struct fscache_object *(*lookup_object)(struct fscache_cache *cache,
+ struct fscache_object *parent,
+ struct fscache_cookie *cookie)
+
+ This method is used to look up an object in the specified cache, given a
+ pointer to the parent object and the cookie to which the object will be
+ attached. This should instantiate that object in the cache if it can, or
+ return -ENOBUFS or -ENOMEM if it can't.
+
+ (*) Increment object refcount [mandatory]:
+
+ struct fscache_object *(*grab_object)(struct fscache_object *object)
+
+ This method is called to increment the reference count on an object. It
+ may fail (for instance if the cache is being withdrawn) by returning NULL.
+ It should return the object pointer if successful.
+
+ (*) Lock/Unlock object [mandatory]:
+
+ void (*lock_object)(struct fscache_object *object)
+ void (*unlock_object)(struct fscache_object *object)
+
+ These methods are used to exclusively lock an object. It must be possible
+ to schedule with the lock held, so a spinlock isn't sufficient.
+
+ (*) Pin/Unpin object [optional]:
+
+ int (*pin_object)(struct fscache_object *object)
+ void (*unpin_object)(struct fscache_object *object)
+
+ These methods are used to pin an object into the cache. Once pinned an
+ object cannot be reclaimed to make space. Return -ENOSPC if there's not
+ enough space in the cache to permit this.
+
+ (*) Update object [mandatory]:
+
+ int (*update_object)(struct fscache_object *object)
+
+ This is called to update the index entry for the specified object. The
+ new information should be in object->cookie->netfs_data. This can be
+ obtained by calling object->cookie->def->get_aux()/get_attr().
+
+ (*) Release object reference [mandatory]:
+
+ void (*put_object)(struct fscache_object *object)
+
+ This method is used to discard a reference to an object. The object may
+ be destroyed when all the references held by FS-Cache are released.
+
+ (*) Synchronise a cache [mandatory]:
+
+ void (*sync)(struct fscache_cache *cache)
+
+ This is called to ask the backend to synchronise a cache with its backing
+ device.
+
+ (*) Dissociate a cache [mandatory]:
+
+ void (*dissociate_pages)(struct fscache_cache *cache)
+
+ This is called to ask a cache to perform any page dissociations as part of
+ cache withdrawal.
+
+ (*) Set the data size on a cache file [mandatory]:
+
+ int (*set_i_size)(struct fscache_object *object, loff_t i_size);
+
+ This is called to indicate to the cache the maximum size a file may reach.
+ The cache may use this to reserve space on the cache. It may also return
+ -ENOBUFS to indicate that insufficient space is available to expand the
+ metadata used to track the data. It should return 0 if successful or
+ -ENOMEM or -EIO on error.
+
+ (*) Reserve cache space for an object's data [optional]:
+
+ int (*reserve_space)(struct fscache_object *object, loff_t size);
+
+ This is called to request that cache space be reserved to hold the data
+ for an object and the metadata used to track it. Zero size should be
+ taken as request to cancel a reservation.
+
+ This should return 0 if successful, -ENOSPC if there isn't enough space
+ available, or -ENOMEM or -EIO on other errors.
+
+ The reservation may exceed the size of the object, thus permitting future
+ expansion. If the amount of space consumed by an object would exceed the
+ reservation, it's permitted to refuse requests to allocate pages, but not
+ required. An object may be pruned down to its reservation size if larger
+ than that already.
+
+ (*) Request page be read from cache [mandatory]:
+
+ int (*read_or_alloc_page)(struct fscache_object *object,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+
+ This is called to attempt to read a netfs page from the cache, or to
+ reserve a backing block if not. FS-Cache will have done as much checking
+ as it can before calling, but most of the work belongs to the backend.
+
+ If there's no page in the cache, then -ENODATA should be returned if the
+ backend managed to reserve a backing block; -ENOBUFS, -ENOMEM or -EIO if
+ it didn't.
+
+ If there is a page in the cache, then a read operation should be queued
+ and 0 returned. When the read finishes, end_io_func() should be called
+ with the following arguments:
+
+ (*end_io_func)(object->cookie->netfs_data,
+ page,
+ end_io_data,
+ error);
+
+ The mark_pages_cached() cookie operation should be called for the page if
+ any cache metadata is retained. This will indicate to the netfs that the
+ page needs explicit uncaching. This operation takes a pagevec, thus
+ allowing several pages to be marked at once.
+
+ (*) Request pages be read from cache [mandatory]:
+
+ int (*read_or_alloc_pages)(struct fscache_object *object,
+ struct address_space *mapping,
+ struct list_head *pages,
+ unsigned *nr_pages,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+
+ This is like the previous operation, except it will be handed a list of
+ pages instead of one page. Any pages on which a read operation is started
+ must be added to the page cache for the specified mapping and also to the
+ LRU. Such pages must also be removed from the pages list and nr_pages
+ decremented per page.
+
+ If there was an error such as -ENOMEM, then that should be returned; else
+ if one or more pages couldn't be read or allocated, then -ENOBUFS should
+ be returned; else if one or more pages couldn't be read, then -ENODATA
+ should be returned. If all the pages are dispatched then 0 should be
+ returned.
+
+ (*) Request page be allocated in the cache [mandatory]:
+
+ int (*allocate_page)(struct fscache_object *object,
+ struct page *page,
+ gfp_t gfp)
+
+ This is like read_or_alloc_page(), except that it shouldn't read from the
+ cache, even if there's data there that could be retrieved. It should,
+ however, set up any internal metadata required such that write_page() can
+ write to the cache.
+
+ If there's no backing block available, then -ENOBUFS should be returned
+ (or -ENOMEM or -EIO if there were other problems). If a block is
+ successfully allocated, then the netfs page should be marked and 0
+ returned.
+
+ (*) Request page be written to cache [mandatory]:
+
+ int (*write_page)(struct fscache_object *object,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+
+ This is called to write from a page on which there was a previously
+ successful read_or_alloc_page() call. FS-Cache filters out pages that
+ don't have mappings.
+
+ If there's no backing block available, then -ENOBUFS should be returned
+ (or -ENOMEM or -EIO if there were other problems).
+
+ If the write operation could be queued, then 0 should be returned. When
+ the write completes, end_io_func() should be called with the following
+ arguments:
+
+ (*end_io_func)(object->cookie->netfs_data,
+ page,
+ end_io_data,
+ error);
+
+ (*) Discard retained per-page metadata [mandatory]:
+
+ void (*uncache_pages)(struct fscache_object *object,
+ struct pagevec *pagevec)
+
+ This is called when one or more netfs pages are being evicted from the
+ pagecache. The cache backend should tear down any internal representation
+ or tracking it maintains.
diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt
new file mode 100644
index 0000000..82c3168
--- /dev/null
+++ b/Documentation/filesystems/caching/fscache.txt
@@ -0,0 +1,151 @@
+ ==========================
+ General Filesystem Caching
+ ==========================
+
+========
+OVERVIEW
+========
+
+This facility is a general purpose cache for network filesystems, though it
+could be used for caching other things such as ISO9660 filesystems too.
+
+FS-Cache mediates between cache backends (such as CacheFS) and network
+filesystems:
+
+ +---------+
+ | | +--------------+
+ | NFS |--+ | |
+ | | | +-->| CacheFS |
+ +---------+ | +----------+ | | /dev/hda5 |
+ | | | | +--------------+
+ +---------+ +-->| | |
+ | | | |--+
+ | AFS |----->| FS-Cache |
+ | | | |--+
+ +---------+ +-->| | |
+ | | | | +--------------+
+ +---------+ | +----------+ | | |
+ | | | +-->| CacheFiles |
+ | ISOFS |--+ | /var/cache |
+ | | +--------------+
+ +---------+
+
+
+FS-Cache does not follow the idea of completely loading every netfs file
+opened in its entirety into a cache before permitting it to be accessed and
+then serving the pages out of that cache rather than the netfs inode because:
+
+ (1) It must be practical to operate without a cache.
+
+ (2) The size of any accessible file must not be limited to the size of the
+ cache.
+
+ (3) The combined size of all opened files (this includes mapped libraries)
+ must not be limited to the size of the cache.
+
+ (4) The user should not be forced to download an entire file just to do a
+ one-off access of a small portion of it (such as might be done with the
+ "file" program).
+
+It instead serves the cache out in PAGE_SIZE chunks as and when requested by
+the netfs('s) using it.
+
+
+FS-Cache provides the following facilities:
+
+ (1) More than one cache can be used at once. Caches can be selected
+ explicitly by use of tags.
+
+ (2) Caches can be added / removed at any time.
+
+ (3) The netfs is provided with an interface that allows either party to
+ withdraw caching facilities from a file (required for (2)).
+
+ (4) The interface to the netfs returns as few errors as possible, preferring
+ rather to let the netfs remain oblivious.
+
+ (5) Cookies are used to represent indices, files and other objects to the
+ netfs. The simplest cookie is just a NULL pointer - indicating nothing
+ cached there.
+
+ (6) The netfs is allowed to propose - dynamically - any index hierarchy it
+ desires, though it must be aware that the index search function is
+ recursive, stack space is limited, and indices can only be children of
+ indices.
+
+ (7) Data I/O is done direct to and from the netfs's pages. The netfs
+ indicates that page A is at index B of the data-file represented by cookie
+ C, and that it should be read or written. The cache backend may or may
+ not start I/O on that page, but if it does, a netfs callback will be
+ invoked to indicate completion. The I/O may be either synchronous or
+ asynchronous.
+
+ (8) Cookies can be "retired" upon release. At this point FS-Cache will mark
+ them as obsolete and the index hierarchy rooted at that point will get
+ recycled.
+
+ (9) The netfs provides a "match" function for index searches. In addition to
+ saying whether a match was made or not, this can also specify that an
+ entry should be updated or deleted.
+
+
+FS-Cache maintains a virtual indexing tree in which all indices, files, objects
+and pages are kept. Bits of this tree may actually reside in one or more
+caches.
+
+ FSDEF
+ |
+ +------------------------------------+
+ | |
+ NFS AFS
+ | |
+ +--------------------------+ +-----------+
+ | | | |
+ homedir mirror afs.org redhat.com
+ | | |
+ +------------+ +---------------+ +----------+
+ | | | | | |
+ 00001 00002 00007 00125 vol00001 vol00002
+ | | | | |
+ +---+---+ +-----+ +---+ +------+------+ +-----+----+
+ | | | | | | | | | | | | |
+PG0 PG1 PG2 PG0 XATTR PG0 PG1 DIRENT DIRENT DIRENT R/W R/O Bak
+ | |
+ PG0 +-------+
+ | |
+ 00001 00003
+ |
+ +---+---+
+ | | |
+ PG0 PG1 PG2
+
+In the example above, you can see two netfs's being backed: NFS and AFS. These
+have different index hierarchies:
+
+ (*) The NFS primary index contains per-server indices. Each server index is
+ indexed by NFS file handles to get data file objects. Each data file
+ objects can have an array of pages, but may also have further child
+ objects, such as extended attributes and directory entries. Extended
+ attribute objects themselves have page-array contents.
+
+ (*) The AFS primary index contains per-cell indices. Each cell index contains
+ per-logical-volume indices. Each of volume index contains up to three
+ indices for the read-write, read-only and backup mirrors of those volumes.
+ Each of these contains vnode data file objects, each of which contains an
+ array of pages.
+
+The very top index is the FS-Cache master index in which individual netfs's
+have entries.
+
+Any index object may reside in more than one cache, provided it only has index
+children. Any index with non-index object children will be assumed to only
+reside in one cache.
+
+
+The netfs API to FS-Cache can be found in:
+
+ Documentation/filesystems/caching/netfs-api.txt
+
+The cache backend API to FS-Cache can be found in:
+
+ Documentation/filesystems/caching/backend-api.txt
diff --git a/Documentation/filesystems/caching/netfs-api.txt b/Documentation/filesystems/caching/netfs-api.txt
new file mode 100644
index 0000000..db9a880
--- /dev/null
+++ b/Documentation/filesystems/caching/netfs-api.txt
@@ -0,0 +1,726 @@
+ ===============================
+ FS-CACHE NETWORK FILESYSTEM API
+ ===============================
+
+There's an API by which a network filesystem can make use of the FS-Cache
+facilities. This is based around a number of principles:
+
+ (1) Caches can store a number of different object types. There are two main
+ object types: indices and files. The first is a special type used by
+ FS-Cache to make finding objects faster and to make retiring of groups of
+ objects easier.
+
+ (2) Every index, file or other object is represented by a cookie. This cookie
+ may or may not have anything associated with it, but the netfs doesn't
+ need to care.
+
+ (3) Barring the top-level index (one entry per cached netfs), the index
+ hierarchy for each netfs is structured according the whim of the netfs.
+
+This API is declared in <linux/fscache.h>.
+
+This document contains the following sections:
+
+ (1) Network filesystem definition
+ (2) Index definition
+ (3) Object definition
+ (4) Network filesystem (un)registration
+ (5) Cache tag lookup
+ (6) Index registration
+ (7) Data file registration
+ (8) Miscellaneous object registration
+ (9) Setting the data file size
+ (10) Page alloc/read/write
+ (11) Page uncaching
+ (12) Index and data file update
+ (13) Miscellaneous cookie operations
+ (14) Cookie unregistration
+ (15) Index and data file invalidation
+
+
+=============================
+NETWORK FILESYSTEM DEFINITION
+=============================
+
+FS-Cache needs a description of the network filesystem. This is specified
+using a record of the following structure:
+
+ struct fscache_netfs {
+ uint32_t version;
+ const char *name;
+ struct fscache_netfs_operations *ops;
+ struct fscache_cookie *primary_index;
+ ...
+ };
+
+This first three fields should be filled in before registration, and the fourth
+will be filled in by the registration function; any other fields should just be
+ignored and are for internal use only.
+
+The fields are:
+
+ (1) The name of the netfs (used as the key in the toplevel index).
+
+ (2) The version of the netfs (if the name matches but the version doesn't, the
+ entire in-cache hierarchy for this netfs will be scrapped and begun
+ afresh).
+
+ (3) The operations table is defined as follows:
+
+ struct fscache_netfs_operations {
+ };
+
+ Currently there aren't any functions here.
+
+ (4) The cookie representing the primary index will be allocated according to
+ another parameter passed into the registration function.
+
+For example, kAFS (linux/fs/afs/) uses the following definitions to describe
+itself:
+
+ static struct fscache_netfs_operations afs_cache_ops = {
+ };
+
+ struct fscache_netfs afs_cache_netfs = {
+ .version = 0,
+ .name = "afs",
+ .ops = &afs_cache_ops,
+ };
+
+
+================
+INDEX DEFINITION
+================
+
+Indices are used for two purposes:
+
+ (1) To aid the finding of a file based on a series of keys (such as AFS's
+ "cell", "volume ID", "vnode ID").
+
+ (2) To make it easier to discard a subset of all the files cached based around
+ a particular key - for instance to mirror the removal of an AFS volume.
+
+However, since it's unlikely that any two netfs's are going to want to define
+their index hierarchies in quite the same way, FS-Cache tries to impose as few
+restraints as possible on how an index is structured and where it is placed in
+the tree. The netfs can even mix indices and data files at the same level, but
+it's not recommended.
+
+Each index entry consists of a key of indeterminate length plus some auxilliary
+data, also of indeterminate length.
+
+There are some limits on indices:
+
+ (1) Any index containing non-index objects should be restricted to a single
+ cache. Any such objects created within an index will be created in the
+ first cache only. The cache in which an index is created can be
+ controlled by cache tags (see below).
+
+ (2) The entry data must be atomically journallable, so it is limited to about
+ 400 bytes at present. At least 400 bytes will be available.
+
+ (3) The depth of the index tree should be judged with care as the search
+ function is recursive. Too many layers will run the kernel out of stack.
+
+
+=================
+OBJECT DEFINITION
+=================
+
+To define an object, a structure of the following type should be filled out:
+
+ struct fscache_object_def
+ {
+ uint8_t name[16];
+ uint8_t type;
+
+ struct fscache_cache_tag *(*select_cache)(
+ const void *parent_netfs_data,
+ const void *cookie_netfs_data);
+
+ uint16_t (*get_key)(const void *cookie_netfs_data,
+ void *buffer,
+ uint16_t bufmax);
+
+ void (*get_attr)(const void *cookie_netfs_data,
+ uint64_t *size);
+
+ uint16_t (*get_aux)(const void *cookie_netfs_data,
+ void *buffer,
+ uint16_t bufmax);
+
+ fscache_checkaux_t (*check_aux)(void *cookie_netfs_data,
+ const void *data,
+ uint16_t datalen);
+
+ void (*mark_pages_cached)(void *cookie_netfs_data,
+ struct address_space *mapping,
+ struct pagevec *cached_pvec);
+
+ void (*now_uncached)(void *cookie_netfs_data);
+ };
+
+This has the following fields:
+
+ (1) The type of the object [mandatory].
+
+ This is one of the following values:
+
+ (*) FSCACHE_COOKIE_TYPE_INDEX
+
+ This defines an index, which is a special FS-Cache type.
+
+ (*) FSCACHE_COOKIE_TYPE_DATAFILE
+
+ This defines an ordinary data file.
+
+ (*) Any other value between 2 and 255
+
+ This defines an extraordinary object such as an XATTR.
+
+ (2) The name of the object type (NUL terminated unless all 16 chars are used)
+ [optional].
+
+ (3) A function to select the cache in which to store an index [optional].
+
+ This function is invoked when an index needs to be instantiated in a cache
+ during the instantiation of a non-index object. Only the immediate index
+ parent for the non-index object will be queried. Any indices above that
+ in the hierarchy may be stored in multiple caches. This function does not
+ need to be supplied for any non-index object or any index that will only
+ have index children.
+
+ If this function is not supplied or if it returns NULL then the first
+ cache in the parent's list will be chosed, or failing that, the first
+ cache in the master list.
+
+ (4) A function to retrieve an object's key from the netfs [mandatory].
+
+ This function will be called with the netfs data that was passed to the
+ cookie acquisition function and the maximum length of key data that it may
+ provide. It should write the required key data into the given buffer and
+ return the quantity it wrote.
+
+ (5) A function to retrieve attribute data from the netfs [optional].
+
+ This function will be called with the netfs data that was passed to the
+ cookie acquisition function. It should return the size of the file if
+ this is a data file. The size may be used to govern how much cache must
+ be reserved for this file in the cache.
+
+ If the function is absent, a file size of 0 is assumed.
+
+ (6) A function to retrieve auxilliary data from the netfs [optional].
+
+ This function will be called with the netfs data that was passed to the
+ cookie acquisition function and the maximum length of auxilliary data that
+ it may provide. It should write the auxilliary data into the given buffer
+ and return the quantity it wrote.
+
+ If this function is absent, the auxilliary data length will be set to 0.
+
+ The length of the auxilliary data buffer may be dependent on the key
+ length. A netfs mustn't rely on being able to provide more than 400 bytes
+ for both.
+
+ (7) A function to check the auxilliary data [optional].
+
+ This function will be called to check that a match found in the cache for
+ this object is valid. For instance with AFS it could check the auxilliary
+ data against the data version number returned by the server to determine
+ whether the index entry in a cache is still valid.
+
+ If this function is absent, it will be assumed that matching objects in a
+ cache are always valid.
+
+ If present, the function should return one of the following values:
+
+ (*) FSCACHE_CHECKAUX_OKAY - the entry is okay as is
+ (*) FSCACHE_CHECKAUX_NEEDS_UPDATE - the entry requires update
+ (*) FSCACHE_CHECKAUX_OBSOLETE - the entry should be deleted
+
+ This function can also be used to extract data from the auxilliary data in
+ the cache and copy it into the netfs's structures.
+
+ (8) A function to mark a page as retaining cache metadata [mandatory].
+
+ This is called by the cache to indicate that it is retaining in-memory
+ information for this page and that the netfs should uncache the page when
+ it has finished. This does not indicate whether there's data on the disk
+ or not. Note that several pages at once may be presented for marking.
+
+ kAFS and NFS use the PG_private bit on the page structure for this, but
+ that may not be appropriate in all cases.
+
+ This function is not required for indices as they're not permitted data.
+
+ (9) A function to unmark all the pages retaining cache metadata [mandatory].
+
+ This is called by FS-Cache to indicate that a backing store is being
+ unbound from a cookie and that all the marks on the pages should be
+ cleared to prevent confusion. Note that the cache will have torn down all
+ its tracking information so that the pages don't need to be explicitly
+ uncached.
+
+ This function is not required for indices as they're not permitted data.
+
+
+===================================
+NETWORK FILESYSTEM (UN)REGISTRATION
+===================================
+
+The first step is to declare the network filesystem to the cache. This also
+involves specifying the layout of the primary index (for AFS, this would be the
+"cell" level).
+
+The registration function is:
+
+ int fscache_register_netfs(struct fscache_netfs *netfs);
+
+It just takes a pointer to the netfs definition. It returns 0 or an error as
+appropriate.
+
+For kAFS, registration is done as follows:
+
+ ret = fscache_register_netfs(&afs_cache_netfs);
+
+The last step is, of course, unregistration:
+
+ void fscache_unregister_netfs(struct fscache_netfs *netfs);
+
+
+================
+CACHE TAG LOOKUP
+================
+
+FS-Cache permits the use of more than one cache. To permit particular index
+subtrees to be bound to particular caches, the second step is to look up cache
+representation tags. This step is optional; it can be left entirely up to
+FS-Cache as to which cache should be used. The problem with doing that is that
+FS-Cache will always pick the first cache that was registered.
+
+To get the representation for a named tag:
+
+ struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name);
+
+This takes a text string as the name and returns a representation of a tag. It
+will never return an error. It may return a dummy tag, however, if it runs out
+of memory; this will inhibit caching with this tag.
+
+Any representation so obtained must be released by passing it to this function:
+
+ void fscache_release_cache_tag(struct fscache_cache_tag *tag);
+
+The tag will be retrieved by FS-Cache when it calls the object definition
+operation select_cache().
+
+
+==================
+INDEX REGISTRATION
+==================
+
+The third step is to inform FS-Cache about part of an index hierarchy that can
+be used to locate files. This is done by requesting a cookie for each index in
+the path to the file:
+
+ struct fscache_cookie *
+ fscache_acquire_cookie(struct fscache_cookie *parent,
+ struct fscache_object_def *def,
+ void *netfs_data);
+
+This function creates an index entry in the index represented by parent,
+filling in the index entry by calling the operations pointed to by def.
+
+Note that this function never returns an error - all errors are handled
+internally. It may also return FSCACHE_NEGATIVE_COOKIE. It is quite
+acceptable to pass this token back to this function as the parent to another
+acquisition (or even to the relinquish cookie, read page and write page
+functions - see below).
+
+Note also that no indices are actually created in a cache until a non-index
+object needs to be created somewhere down the hierarchy. Furthermore, an index
+may be created in several different caches independently at different times.
+This is all handled transparently, and the netfs doesn't see any of it.
+
+For example, with AFS, a cell would be added to the primary index. This index
+entry would have a dependent inode containing a volume location index for the
+volume mappings within this cell:
+
+ cell->cache =
+ fscache_acquire_cookie(afs_cache_netfs.primary_index,
+ &afs_cell_cache_index_def,
+ cell);
+
+Then when a volume location was accessed, it would be entered into the cell's
+index and an inode would be allocated that acts as a volume type and hash chain
+combination:
+
+ vlocation->cache =
+ fscache_acquire_cookie(cell->cache,
+ &afs_vlocation_cache_index_def,
+ vlocation);
+
+And then a particular flavour of volume (R/O for example) could be added to
+that index, creating another index for vnodes (AFS inode equivalents):
+
+ volume->cache =
+ fscache_acquire_cookie(vlocation->cache,
+ &afs_volume_cache_index_def,
+ volume);
+
+
+======================
+DATA FILE REGISTRATION
+======================
+
+The fourth step is to request a data file be created in the cache. This is
+identical to index cookie acquisition. The only difference is that the type in
+the object definition should be something other than index type.
+
+ vnode->cache =
+ fscache_acquire_cookie(volume->cache,
+ &afs_vnode_cache_object_def,
+ vnode);
+
+
+=================================
+MISCELLANEOUS OBJECT REGISTRATION
+=================================
+
+An optional step is to request an object of miscellaneous type be created in
+the cache. This is almost identical to index cookie acquisition. The only
+difference is that the type in the object definition should be something other
+than index type. Whilst the parent object could be an index, it's more likely
+it would be some other type of object such as a data file.
+
+ xattr->cache =
+ fscache_acquire_cookie(vnode->cache,
+ &afs_xattr_cache_object_def,
+ xattr);
+
+Miscellaneous objects might be used to store extended attributes or directory
+entries for example.
+
+
+==========================
+SETTING THE DATA FILE SIZE
+==========================
+
+The fifth step is to set the size of the file. This doesn't automatically
+reserve any space in the cache, but permits the cache to adjust its metadata
+for data tracking appropriately:
+
+ int fscache_set_i_size(struct fscache_cookie *cookie, loff_t i_size);
+
+The cache will return -ENOBUFS if there is no backing cache or if there is no
+space to allocate any extra metadata required in the cache.
+
+Note that attempts to read or write data pages in the cache over this size may
+be rebuffed with -ENOBUFS.
+
+
+=====================
+PAGE READ/ALLOC/WRITE
+=====================
+
+And the sixth step is to store and retrieve pages in the cache. There are
+three functions that are used to do this.
+
+Note:
+
+ (1) A page should not be re-read or re-allocated without uncaching it first.
+
+ (2) A read or allocated page must be uncached when the netfs page is released
+ from the pagecache.
+
+ (3) A page should only be written to the cache if previous read or allocated.
+
+This permits the cache to maintain its page tracking in proper order.
+
+
+PAGE READ
+---------
+
+Firstly, the netfs should ask FS-Cache to examine the caches and read the
+contents cached for a particular page of a particular file if present, or else
+allocate space to store the contents if not:
+
+ typedef
+ void (*fscache_rw_complete_t)(void *cookie_data,
+ struct page *page,
+ void *end_io_data,
+ int error);
+
+ int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp);
+
+The cookie argument must specify a cookie for an object that isn't an index,
+the page specified will have the data loaded into it (and is also used to
+specify the page number), and the gfp argument is used to control how any
+memory allocations made are satisfied.
+
+If the cookie indicates the inode is not cached:
+
+ (1) The function will return -ENOBUFS.
+
+Else if there's a copy of the page resident in the cache:
+
+ (1) The mark_pages_cached() cookie operation will be called on that page.
+
+ (2) The function will submit a request to read the data from the cache's
+ backing device directly into the page specified.
+
+ (3) The function will return 0.
+
+ (4) When the read is complete, end_io_func() will be invoked with:
+
+ (*) The netfs data supplied when the cookie was created.
+
+ (*) The page descriptor.
+
+ (*) The end_io_data argument passed to the above function.
+
+ (*) An argument that's 0 on success or negative for an error code.
+
+ If an error occurs, it should be assumed that the page contains no usable
+ data.
+
+Otherwise, if there's not a copy available in cache, but the cache may be able
+to store the page:
+
+ (1) The mark_pages_cached() cookie operation will be called on that page.
+
+ (2) A block may be reserved in the cache and attached to the object at the
+ appropriate place.
+
+ (3) The function will return -ENODATA.
+
+This function may also return -ENOMEM or -EINTR, in which case it won't have
+read any data from the cache.
+
+
+PAGE ALLOCATE
+-------------
+
+Alternatively, if there's not expected to be any data in the cache for a page
+because the file has been extended, a block can simply be allocated instead:
+
+ int fscache_alloc_page(struct fscache_cookie *cookie,
+ struct page *page,
+ gfp_t gfp);
+
+This is similar to the fscache_read_or_alloc_page() function, except that it
+never reads from the cache. It will return 0 if a block has been allocated,
+rather than -ENODATA as the other would. One or the other must be performed
+before writing to the cache.
+
+The mark_pages_cached() cookie operation will be called on the page if
+successful.
+
+
+PAGE WRITE
+----------
+
+Secondly, if the netfs changes the contents of the page (either due to an
+initial download or if a user performs a write), then the page should be
+written back to the cache:
+
+ int fscache_write_page(struct fscache_cookie *cookie,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp);
+
+The cookie argument must specify a data file cookie, the page specified should
+contain the data to be written (and is also used to specify the page number),
+and the gfp argument is used to control how any memory allocations made are
+satisfied.
+
+The page must have first been read or allocated successfully and must not have
+been uncached before writing is performed.
+
+If the cookie indicates the inode is not cached then:
+
+ (1) The function will return -ENOBUFS.
+
+Else if space can be allocated in the cache to hold this page:
+
+ (1) The function will submit a request to write the data to cache's backing
+ device directly from the page specified.
+
+ (2) The function will return 0.
+
+ (3) When the write is complete the end_io_func() will be invoked with:
+
+ (*) The netfs data supplied when the cookie was created.
+
+ (*) The page descriptor.
+
+ (*) The end_io_data argument passed to the function.
+
+ (*) An argument that's 0 on success or negative for an error.
+
+ If an error occurs, it can be assumed that the page has not been written
+ to the cache, and that either there's a block containing the old data or
+ no block at all in the cache.
+
+Else if there's no space available in the cache, -ENOBUFS will be returned.
+
+
+MULTIPLE PAGE READ
+------------------
+
+A facility is provided to read several pages at once, as requested by the
+readpages() address space operation:
+
+ int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
+ struct address_space *mapping,
+ struct list_head *pages,
+ int *nr_pages,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp);
+
+This works in a similar way to fscache_read_or_alloc_page(), except:
+
+ (1) Any page it can retrieve data for is removed from pages and nr_pages and
+ dispatched for reading to the disk. Reads of adjacent pages on disk may
+ be merged for greater efficiency.
+
+ (2) The mark_pages_cached() cookie operation will be called on several pages
+ at once if they're being read or allocated.
+
+ (3) If there was an general error, then that error will be returned.
+
+ Else if some pages couldn't be allocated or read, then -ENOBUFS will be
+ returned.
+
+ Else if some pages couldn't be read but were allocated, then -ENODATA will
+ be returned.
+
+ Otherwise, if all pages had reads dispatched, then 0 will be returned, the
+ list will be empty and *nr_pages will be 0.
+
+ (4) end_io_func will be called once for each page being read as the reads
+ complete.
+
+Note that a return of -ENODATA, -ENOBUFS or any other error does not preclude
+some of the pages being read and some being allocated. Those pages will have
+been marked appropriately and will need uncaching.
+
+
+==============
+PAGE UNCACHING
+==============
+
+To uncache a page, this function should be called:
+
+ void fscache_uncache_page(struct fscache_cookie *cookie,
+ struct page *page);
+
+This function permits the cache to release any in-memory representation it
+might be holding for this netfs page. This function must be called once for
+each page on which the read or write page functions above have been called to
+make sure the cache's in-memory tracking information gets torn down.
+
+Note that pages can't be explicitly deleted from the a data file. The whole
+data file must be retired (see the relinquish cookie function below).
+
+Furthermore, note that this does not cancel the asynchronous read or write
+operation started by the read/alloc and write functions.
+
+There is another unbinding operation similar to the above that takes a set of
+pages to unbind in one go:
+
+ void fscache_uncache_pagevec(struct fscache_cookie *cookie,
+ struct pagevec *pagevec);
+
+
+==========================
+INDEX AND DATA FILE UPDATE
+==========================
+
+To request an update of the index data for an index or other object, the
+following function should be called:
+
+ void fscache_update_cookie(struct fscache_cookie *cookie);
+
+This function will refer back to the netfs_data pointer stored in the cookie by
+the acquisition function to obtain the data to write into each revised index
+entry. The update method in the parent index definition will be called to
+transfer the data.
+
+Note that partial updates may happen automatically at other times, such as when
+data blocks are added to a data file object.
+
+
+===============================
+MISCELLANEOUS COOKIE OPERATIONS
+===============================
+
+There are a number of operations that can be used to control cookies:
+
+ (*) Cookie pinning:
+
+ int fscache_pin_cookie(struct fscache_cookie *cookie);
+ void fscache_unpin_cookie(struct fscache_cookie *cookie);
+
+ These operations permit data cookies to be pinned into the cache and to
+ have the pinning removed. They are not permitted on index cookies.
+
+ The pinning function will return 0 if successful, -ENOBUFS in the cookie
+ isn't backed by a cache, -EOPNOTSUPP if the cache doesn't support pinning,
+ -ENOSPC if there isn't enough space to honour the operation, -ENOMEM or
+ -EIO if there's any other problem.
+
+ (*) Data space reservation:
+
+ int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size);
+
+ This permits a netfs to request cache space be reserved to store up to the
+ given amount of a file. It is permitted to ask for more than the current
+ size of the file to allow for future file expansion.
+
+ If size is given as zero then the reservation will be cancelled.
+
+ The function will return 0 if successful, -ENOBUFS in the cookie isn't
+ backed by a cache, -EOPNOTSUPP if the cache doesn't support reservations,
+ -ENOSPC if there isn't enough space to honour the operation, -ENOMEM or
+ -EIO if there's any other problem.
+
+ Note that this doesn't pin an object in a cache; it can still be culled to
+ make space if it's not in use.
+
+
+=====================
+COOKIE UNREGISTRATION
+=====================
+
+To get rid of a cookie, this function should be called.
+
+ void fscache_relinquish_cookie(struct fscache_cookie *cookie,
+ int retire);
+
+If retire is non-zero, then the object will be marked for recycling, and all
+copies of it will be removed from all active caches in which it is present.
+Not only that but all child objects will also be retired.
+
+If retire is zero, then the object may be available again when next the
+acquisition function is called. Retirement here will overrule the pinning on a
+cookie.
+
+One very important note - relinquish must NOT be called for a cookie unless all
+the cookies for "child" indices, objects and pages have been relinquished
+first.
+
+
+================================
+INDEX AND DATA FILE INVALIDATION
+================================
+
+There is no direct way to invalidate an index subtree or a data file. To do
+this, the caller should relinquish and retire the cookie they have, and then
+acquire a new one.
diff --git a/fs/Kconfig b/fs/Kconfig
index f9b5842..66acf29 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -508,6 +508,21 @@ config FUSE_FS
If you want to develop a userspace FS, or if you want to use
a filesystem based on FUSE, answer Y or M.
+menu "Caches"
+
+config FSCACHE
+ tristate "General filesystem cache manager"
+ depends on EXPERIMENTAL
+ help
+ This option enables a generic filesystem caching manager that can be
+ used by various network and other filesystems to cache data
+ locally. Different sorts of caches can be plugged in, depending on the
+ resources available.
+
+ See Documentation/filesystems/caching/fscache.txt for more information.
+
+endmenu
+
menu "CD-ROM/DVD Filesystems"
config ISO9660_FS
diff --git a/fs/Makefile b/fs/Makefile
index 83bf478..36ee03b 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -50,6 +50,7 @@ obj-y += devpts/
obj-$(CONFIG_PROFILING) += dcookies.o
# Do not add any filesystems before this line
+obj-$(CONFIG_FSCACHE) += fscache/
obj-$(CONFIG_REISERFS_FS) += reiserfs/
obj-$(CONFIG_EXT3_FS) += ext3/ # Before ext2 so root fs can be ext3
obj-$(CONFIG_JBD) += jbd/
diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile
new file mode 100644
index 0000000..10f17a3
--- /dev/null
+++ b/fs/fscache/Makefile
@@ -0,0 +1,11 @@
+#
+# Makefile for general filesystem caching code
+#
+
+fscache-objs := \
+ cookie.o \
+ fsdef.o \
+ main.o \
+ page.o
+
+obj-$(CONFIG_FSCACHE) := fscache.o
diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
new file mode 100644
index 0000000..98cf6a9
--- /dev/null
+++ b/fs/fscache/cookie.c
@@ -0,0 +1,1063 @@
+/* cookie.c: general filesystem cache cookie management
+ *
+ * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells at redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include "fscache-int.h"
+
+static LIST_HEAD(fscache_cache_tag_list);
+static LIST_HEAD(fscache_cache_list);
+static LIST_HEAD(fscache_netfs_list);
+static DECLARE_RWSEM(fscache_addremove_sem);
+static struct fscache_cache_tag fscache_nomem_tag;
+
+kmem_cache_t *fscache_cookie_jar;
+
+static void fscache_withdraw_object(struct fscache_cache *cache,
+ struct fscache_object *object);
+
+static void __fscache_cookie_put(struct fscache_cookie *cookie);
+
+static inline void fscache_cookie_put(struct fscache_cookie *cookie)
+{
+ /* check to see whether the cookie has already been released by looking
+ * for the poison when slab debugging is on */
+#ifdef CONFIG_DEBUG_SLAB
+ BUG_ON((atomic_read(&cookie->usage) & 0xffff0000) == 0x6b6b0000);
+#endif
+
+ BUG_ON(atomic_read(&cookie->usage) <= 0);
+
+ if (atomic_dec_and_test(&cookie->usage))
+ __fscache_cookie_put(cookie);
+
+}
+
+/*****************************************************************************/
+/*
+ * look up a cache tag
+ */
+struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *name)
+{
+ struct fscache_cache_tag *tag, *xtag;
+
+ /* firstly check for the existence of the tag under read lock */
+ down_read(&fscache_addremove_sem);
+
+ list_for_each_entry(tag, &fscache_cache_tag_list, link) {
+ if (strcmp(tag->name, name) == 0) {
+ atomic_inc(&tag->usage);
+ up_read(&fscache_addremove_sem);
+ return tag;
+ }
+ }
+
+ up_read(&fscache_addremove_sem);
+
+ /* the tag does not exist - create a candidate */
+ xtag = kmalloc(sizeof(*xtag) + strlen(name) + 1, GFP_KERNEL);
+ if (!xtag)
+ /* return a dummy tag if out of memory */
+ return &fscache_nomem_tag;
+
+ atomic_set(&xtag->usage, 1);
+ strcpy(xtag->name, name);
+
+ /* write lock, search again and add if still not present */
+ down_write(&fscache_addremove_sem);
+
+ list_for_each_entry(tag, &fscache_cache_tag_list, link) {
+ if (strcmp(tag->name, name) == 0) {
+ atomic_inc(&tag->usage);
+ up_write(&fscache_addremove_sem);
+ kfree(xtag);
+ return tag;
+ }
+ }
+
+ list_add_tail(&xtag->link, &fscache_cache_tag_list);
+ up_write(&fscache_addremove_sem);
+ return xtag;
+
+} /* end __fscache_lookup_cache_tag() */
+
+/*****************************************************************************/
+/*
+ * release a reference to a cache tag
+ */
+void __fscache_release_cache_tag(struct fscache_cache_tag *tag)
+{
+ if (tag != &fscache_nomem_tag) {
+ down_write(&fscache_addremove_sem);
+
+ if (atomic_dec_and_test(&tag->usage))
+ list_del_init(&tag->link);
+ else
+ tag = NULL;
+
+ up_write(&fscache_addremove_sem);
+
+ kfree(tag);
+ }
+
+} /* end __fscache_release_cache_tag() */
+
+/*****************************************************************************/
+/*
+ * register a network filesystem for caching
+ */
+int __fscache_register_netfs(struct fscache_netfs *netfs)
+{
+ struct fscache_netfs *ptr;
+ int ret;
+
+ _enter("{%s}", netfs->name);
+
+ INIT_LIST_HEAD(&netfs->link);
+
+ /* allocate a cookie for the primary index */
+ netfs->primary_index =
+ kmem_cache_zalloc(fscache_cookie_jar, SLAB_KERNEL);
+
+ if (!netfs->primary_index) {
+ _leave(" = -ENOMEM");
+ return -ENOMEM;
+ }
+
+ /* initialise the primary index cookie */
+ atomic_set(&netfs->primary_index->usage, 1);
+ atomic_set(&netfs->primary_index->children, 0);
+
+ netfs->primary_index->def = &fscache_fsdef_netfs_def;
+ netfs->primary_index->parent = &fscache_fsdef_index;
+ netfs->primary_index->netfs = netfs;
+ netfs->primary_index->netfs_data = netfs;
+
+ atomic_inc(&netfs->primary_index->parent->usage);
+ atomic_inc(&netfs->primary_index->parent->children);
+
+ init_rwsem(&netfs->primary_index->sem);
+ INIT_HLIST_HEAD(&netfs->primary_index->backing_objects);
+
+ /* check the netfs type is not already present */
+ down_write(&fscache_addremove_sem);
+
+ ret = -EEXIST;
+ list_for_each_entry(ptr, &fscache_netfs_list, link) {
+ if (strcmp(ptr->name, netfs->name) == 0)
+ goto already_registered;
+ }
+
+ list_add(&netfs->link, &fscache_netfs_list);
+ ret = 0;
+
+ printk("FS-Cache: netfs '%s' registered for caching\n", netfs->name);
+
+already_registered:
+ up_write(&fscache_addremove_sem);
+
+ if (ret < 0) {
+ netfs->primary_index->parent = NULL;
+ __fscache_cookie_put(netfs->primary_index);
+ netfs->primary_index = NULL;
+ }
+
+ _leave(" = %d", ret);
+ return ret;
+
+} /* end __fscache_register_netfs() */
+
+EXPORT_SYMBOL(__fscache_register_netfs);
+
+/*****************************************************************************/
+/*
+ * unregister a network filesystem from the cache
+ * - all cookies must have been released first
+ */
+void __fscache_unregister_netfs(struct fscache_netfs *netfs)
+{
+ _enter("{%s.%u}", netfs->name, netfs->version);
+
+ down_write(&fscache_addremove_sem);
+
+ list_del(&netfs->link);
+ fscache_relinquish_cookie(netfs->primary_index, 0);
+
+ up_write(&fscache_addremove_sem);
+
+ printk("FS-Cache: netfs '%s' unregistered from caching\n",
+ netfs->name);
+
+ _leave("");
+
+} /* end __fscache_unregister_netfs() */
+
+EXPORT_SYMBOL(__fscache_unregister_netfs);
+
+/*****************************************************************************/
+/*
+ * initialise a cache record
+ */
+void fscache_init_cache(struct fscache_cache *cache,
+ struct fscache_cache_ops *ops,
+ const char *idfmt,
+ ...)
+{
+ va_list va;
+
+ memset(cache, 0, sizeof(*cache));
+
+ cache->ops = ops;
+
+ va_start(va, idfmt);
+ vsnprintf(cache->identifier, sizeof(cache->identifier), idfmt, va);
+ va_end(va);
+
+ INIT_LIST_HEAD(&cache->link);
+ INIT_LIST_HEAD(&cache->object_list);
+ spin_lock_init(&cache->object_list_lock);
+ init_rwsem(&cache->withdrawal_sem);
+
+} /* end fscache_init_cache() */
+
+EXPORT_SYMBOL(fscache_init_cache);
+
+/*****************************************************************************/
+/*
+ * declare a mounted cache as being open for business
+ */
+int fscache_add_cache(struct fscache_cache *cache,
+ struct fscache_object *ifsdef,
+ const char *tagname)
+{
+ struct fscache_cache_tag *tag;
+
+ BUG_ON(!cache->ops);
+ BUG_ON(!ifsdef);
+
+ cache->flags = 0;
+
+ if (!tagname)
+ tagname = cache->identifier;
+
+ BUG_ON(!tagname[0]);
+
+ _enter("{%s.%s},,%s", cache->ops->name, cache->identifier, tagname);
+
+ if (!cache->ops->grab_object(ifsdef))
+ BUG();
+
+ ifsdef->cookie = &fscache_fsdef_index;
+ ifsdef->cache = cache;
+ cache->fsdef = ifsdef;
+
+ down_write(&fscache_addremove_sem);
+
+ /* instantiate or allocate a cache tag */
+ list_for_each_entry(tag, &fscache_cache_tag_list, link) {
+ if (strcmp(tag->name, tagname) == 0) {
+ if (tag->cache) {
+ printk(KERN_ERR
+ "FS-Cache: cache tag '%s' already in use\n",
+ tagname);
+ up_write(&fscache_addremove_sem);
+ return -EEXIST;
+ }
+
+ atomic_inc(&tag->usage);
+ goto found_cache_tag;
+ }
+ }
+
+ tag = kmalloc(sizeof(*tag) + strlen(tagname) + 1, GFP_KERNEL);
+ if (!tag) {
+ up_write(&fscache_addremove_sem);
+ return -ENOMEM;
+ }
+
+ atomic_set(&tag->usage, 1);
+ strcpy(tag->name, tagname);
+ list_add_tail(&tag->link, &fscache_cache_tag_list);
+
+found_cache_tag:
+ tag->cache = cache;
+ cache->tag = tag;
+
+ /* add the cache to the list */
+ list_add(&cache->link, &fscache_cache_list);
+
+ /* add the cache's netfs definition index object to the cache's
+ * list */
+ spin_lock(&cache->object_list_lock);
+ list_add_tail(&ifsdef->cache_link, &cache->object_list);
+ spin_unlock(&cache->object_list_lock);
+
+ /* add the cache's netfs definition index object to the top level index
+ * cookie as a known backing object */
+ down_write(&fscache_fsdef_index.sem);
+
+ hlist_add_head(&ifsdef->cookie_link,
+ &fscache_fsdef_index.backing_objects);
+
+ atomic_inc(&fscache_fsdef_index.usage);
+
+ /* done */
+ up_write(&fscache_fsdef_index.sem);
+ up_write(&fscache_addremove_sem);
+
+ printk(KERN_NOTICE
+ "FS-Cache: Cache \"%s\" added (type %s)\n",
+ cache->tag->name, cache->ops->name);
+
+ _leave(" = 0 [%s]", cache->identifier);
+ return 0;
+
+} /* end fscache_add_cache() */
+
+EXPORT_SYMBOL(fscache_add_cache);
+
+/*****************************************************************************/
+/*
+ * note a cache I/O error
+ */
+void fscache_io_error(struct fscache_cache *cache)
+{
+ set_bit(FSCACHE_IOERROR, &cache->flags);
+
+ printk(KERN_ERR "FS-Cache: Cache %s stopped due to I/O error\n",
+ cache->ops->name);
+
+} /* end fscache_io_error() */
+
+EXPORT_SYMBOL(fscache_io_error);
+
+/*****************************************************************************/
+/*
+ * withdraw an unmounted cache from the active service
+ */
+void fscache_withdraw_cache(struct fscache_cache *cache)
+{
+ struct fscache_object *object;
+
+ _enter("");
+
+ printk(KERN_NOTICE
+ "FS-Cache: Withdrawing cache \"%s\"\n",
+ cache->tag->name);
+
+ /* make the cache unavailable for cookie acquisition */
+ down_write(&cache->withdrawal_sem);
+
+ down_write(&fscache_addremove_sem);
+ list_del_init(&cache->link);
+ cache->tag->cache = NULL;
+ up_write(&fscache_addremove_sem);
+
+ /* mark all objects as being withdrawn */
+ spin_lock(&cache->object_list_lock);
+ list_for_each_entry(object, &cache->object_list, cache_link) {
+ set_bit(FSCACHE_OBJECT_WITHDRAWN, &object->flags);
+ }
+ spin_unlock(&cache->object_list_lock);
+
+ /* make sure all pages pinned by operations on behalf of the netfs are
+ * written to disc */
+ cache->ops->sync_cache(cache);
+
+ /* dissociate all the netfs pages backed by this cache from the block
+ * mappings in the cache */
+ cache->ops->dissociate_pages(cache);
+
+ /* we now have to destroy all the active objects pertaining to this
+ * cache */
+ spin_lock(&cache->object_list_lock);
+
+ while (!list_empty(&cache->object_list)) {
+ object = list_entry(cache->object_list.next,
+ struct fscache_object, cache_link);
+ list_del_init(&object->cache_link);
+ spin_unlock(&cache->object_list_lock);
+
+ _debug("withdraw %p", object->cookie);
+
+ /* we've extracted an active object from the tree - now dispose
+ * of it */
+ fscache_withdraw_object(cache, object);
+
+ spin_lock(&cache->object_list_lock);
+ }
+
+ spin_unlock(&cache->object_list_lock);
+
+ fscache_release_cache_tag(cache->tag);
+ cache->tag = NULL;
+
+ _leave("");
+
+} /* end fscache_withdraw_cache() */
+
+EXPORT_SYMBOL(fscache_withdraw_cache);
+
+/*****************************************************************************/
+/*
+ * withdraw an object from active service at the behest of the cache
+ * - need break the links to a cached object cookie
+ * - called under two situations:
+ * (1) recycler decides to reclaim an in-use object
+ * (2) a cache is unmounted
+ * - have to take care as the cookie can be being relinquished by the netfs
+ * simultaneously
+ * - the active object is pinned by the caller holding a refcount on it
+ */
+static void fscache_withdraw_object(struct fscache_cache *cache,
+ struct fscache_object *object)
+{
+ struct fscache_cookie *cookie, *xcookie = NULL;
+
+ _enter(",%p", object);
+
+ /* first of all we have to break the links between the object and the
+ * cookie
+ * - we have to hold both semaphores BUT we have to get the cookie sem
+ * FIRST
+ */
+ cache->ops->lock_object(object);
+
+ cookie = object->cookie;
+ if (cookie) {
+ /* pin the cookie so that is doesn't escape */
+ atomic_inc(&cookie->usage);
+
+ /* re-order the locks to avoid deadlock */
+ cache->ops->unlock_object(object);
+ down_write(&cookie->sem);
+ cache->ops->lock_object(object);
+
+ /* erase references from the object to the cookie */
+ hlist_del_init(&object->cookie_link);
+
+ xcookie = object->cookie;
+ object->cookie = NULL;
+
+ up_write(&cookie->sem);
+ }
+
+ cache->ops->unlock_object(object);
+
+ /* we've broken the links between cookie and object */
+ if (xcookie) {
+ fscache_cookie_put(xcookie);
+ cache->ops->put_object(object);
+ }
+
+ /* unpin the cookie */
+ if (cookie) {
+ if (cookie->def && cookie->def->now_uncached)
+ cookie->def->now_uncached(cookie->netfs_data);
+ fscache_cookie_put(cookie);
+ }
+
+ _leave("");
+
+} /* end fscache_withdraw_object() */
+
+/*****************************************************************************/
+/*
+ * select a cache on which to store an object
+ * - the cache addremove semaphore must be at least read-locked by the caller
+ * - the object will never be an index
+ */
+static struct fscache_cache *fscache_select_cache_for_object(struct fscache_cookie *cookie)
+{
+ struct fscache_cache_tag *tag;
+ struct fscache_object *object;
+ struct fscache_cache *cache;
+
+ _enter("");
+
+ if (list_empty(&fscache_cache_list)) {
+ _leave(" = NULL [no cache]");
+ return NULL;
+ }
+
+ /* we check the parent to determine the cache to use */
+ down_read(&cookie->parent->sem);
+
+ /* the first in the parent's backing list should be the preferred
+ * cache */
+ if (!hlist_empty(&cookie->parent->backing_objects)) {
+ object = hlist_entry(cookie->parent->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ cache = object->cache;
+ if (test_bit(FSCACHE_IOERROR, &cache->flags))
+ cache = NULL;
+
+ up_read(&cookie->parent->sem);
+ _leave(" = %p [parent]", cache);
+ return cache;
+ }
+
+ /* the parent is unbacked */
+ if (cookie->parent->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
+ /* parent not an index and is unbacked */
+ up_read(&cookie->parent->sem);
+ _leave(" = NULL [parent ubni]");
+ return NULL;
+ }
+
+ up_read(&cookie->parent->sem);
+
+ if (!cookie->parent->def->select_cache)
+ goto no_preference;
+
+ /* ask the netfs for its preference */
+ tag = cookie->parent->def->select_cache(
+ cookie->parent->parent->netfs_data,
+ cookie->parent->netfs_data);
+
+ if (!tag)
+ goto no_preference;
+
+ if (tag == &fscache_nomem_tag) {
+ _leave(" = NULL [nomem tag]");
+ return NULL;
+ }
+
+ if (!tag->cache) {
+ _leave(" = NULL [unbacked tag]");
+ return NULL;
+ }
+
+ if (test_bit(FSCACHE_IOERROR, &tag->cache->flags))
+ return NULL;
+
+ _leave(" = %p [specific]", tag->cache);
+ return tag->cache;
+
+no_preference:
+ /* netfs has no preference - just select first cache */
+ cache = list_entry(fscache_cache_list.next,
+ struct fscache_cache, link);
+ _leave(" = %p [first]", cache);
+ return cache;
+
+} /* end fscache_select_cache_for_object() */
+
+/*****************************************************************************/
+/*
+ * get a backing object for a cookie from the chosen cache
+ * - the cookie must be write-locked by the caller
+ * - all parent indexes will be obtained recursively first
+ */
+static struct fscache_object *fscache_lookup_object(struct fscache_cookie *cookie,
+ struct fscache_cache *cache)
+{
+ struct fscache_cookie *parent = cookie->parent;
+ struct fscache_object *pobject, *object;
+ struct hlist_node *_p;
+
+ _enter("{%s/%s},",
+ parent && parent->def ? parent->def->name : "",
+ cookie->def ? (char *) cookie->def->name : "<file>");
+
+ if (test_bit(FSCACHE_IOERROR, &cache->flags))
+ return NULL;
+
+ /* see if we have the backing object for this cookie + cache immediately
+ * to hand
+ */
+ object = NULL;
+ hlist_for_each_entry(object, _p,
+ &cookie->backing_objects, cookie_link
+ ) {
+ if (object->cache == cache)
+ break;
+ }
+
+ if (object) {
+ _leave(" = %p [old]", object);
+ return object;
+ }
+
+ BUG_ON(!parent); /* FSDEF entries don't have a parent */
+
+ /* we don't have a backing cookie, so we need to consult the object's
+ * parent index in the selected cache and maybe insert an entry
+ * therein; so the first thing to do is make sure that the parent index
+ * is represented on disc
+ */
+ down_read(&parent->sem);
+
+ pobject = NULL;
+ hlist_for_each_entry(pobject, _p,
+ &parent->backing_objects, cookie_link
+ ) {
+ if (pobject->cache == cache)
+ break;
+ }
+
+ if (!pobject) {
+ /* we don't know about the parent object */
+ up_read(&parent->sem);
+ down_write(&parent->sem);
+
+ pobject = fscache_lookup_object(parent, cache);
+ if (IS_ERR(pobject)) {
+ up_write(&parent->sem);
+ _leave(" = %ld [no ipobj]", PTR_ERR(pobject));
+ return pobject;
+ }
+
+ _debug("pobject=%p", pobject);
+
+ BUG_ON(pobject->cookie != parent);
+
+ downgrade_write(&parent->sem);
+ }
+
+ /* now we can attempt to look up this object in the parent, possibly
+ * creating a representation on disc when we do so
+ */
+ object = cache->ops->lookup_object(cache, pobject, cookie);
+ up_read(&parent->sem);
+
+ if (IS_ERR(object)) {
+ _leave(" = %ld [no obj]", PTR_ERR(object));
+ return object;
+ }
+
+ /* keep track of it */
+ cache->ops->lock_object(object);
+
+ BUG_ON(!hlist_unhashed(&object->cookie_link));
+
+ /* attach to the cache's object list */
+ if (list_empty(&object->cache_link)) {
+ spin_lock(&cache->object_list_lock);
+ list_add(&object->cache_link, &cache->object_list);
+ spin_unlock(&cache->object_list_lock);
+ }
+
+ /* attach to the cookie */
+ object->cookie = cookie;
+ atomic_inc(&cookie->usage);
+ hlist_add_head(&object->cookie_link, &cookie->backing_objects);
+
+ /* done */
+ cache->ops->unlock_object(object);
+ _leave(" = %p [new]", object);
+ return object;
+
+} /* end fscache_lookup_object() */
+
+/*****************************************************************************/
+/*
+ * request a cookie to represent an object (index, datafile, xattr, etc)
+ * - parent specifies the parent object
+ * - the top level index cookie for each netfs is stored in the fscache_netfs
+ * struct upon registration
+ * - idef points to the definition
+ * - the netfs_data will be passed to the functions pointed to in *def
+ * - all attached caches will be searched to see if they contain this object
+ * - index objects aren't stored on disk until there's a dependent file that
+ * needs storing
+ * - other objects are stored in a selected cache immediately, and all the
+ * indexes forming the path to it are instantiated if necessary
+ * - we never let on to the netfs about errors
+ * - we may set a negative cookie pointer, but that's okay
+ */
+struct fscache_cookie *__fscache_acquire_cookie(struct fscache_cookie *parent,
+ struct fscache_cookie_def *def,
+ void *netfs_data)
+{
+ struct fscache_cookie *cookie;
+ struct fscache_cache *cache;
+ struct fscache_object *object;
+ int ret = 0;
+
+ BUG_ON(!def);
+
+ _enter("{%s},{%s},%p",
+ parent ? (char *) parent->def->name : "<no-parent>",
+ def->name, netfs_data);
+
+ /* if there's no parent cookie, then we don't create one here either */
+ if (parent == FSCACHE_NEGATIVE_COOKIE) {
+ _leave(" [no parent]");
+ return FSCACHE_NEGATIVE_COOKIE;
+ }
+
+ /* validate the definition */
+ BUG_ON(!def->get_key);
+ BUG_ON(!def->name[0]);
+
+ BUG_ON(def->type == FSCACHE_COOKIE_TYPE_INDEX &&
+ parent->def->type != FSCACHE_COOKIE_TYPE_INDEX);
+
+ /* allocate and initialise a cookie */
+ cookie = kmem_cache_alloc(fscache_cookie_jar, SLAB_KERNEL);
+ if (!cookie) {
+ _leave(" [ENOMEM]");
+ return FSCACHE_NEGATIVE_COOKIE;
+ }
+
+ atomic_set(&cookie->usage, 1);
+ atomic_set(&cookie->children, 0);
+
+ atomic_inc(&parent->usage);
+ atomic_inc(&parent->children);
+
+ cookie->def = def;
+ cookie->parent = parent;
+ cookie->netfs = parent->netfs;
+ cookie->netfs_data = netfs_data;
+
+ /* now we need to see whether the backing objects for this cookie yet
+ * exist, if not there'll be nothing to search */
+ down_read(&fscache_addremove_sem);
+
+ if (list_empty(&fscache_cache_list)) {
+ up_read(&fscache_addremove_sem);
+ _leave(" = %p [no caches]", cookie);
+ return cookie;
+ }
+
+ /* if the object is an index then we need do nothing more here - we
+ * create indexes on disk when we need them as an index may exist in
+ * multiple caches */
+ if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
+ down_write(&cookie->sem);
+
+ /* the object is a file - we need to select a cache in which to
+ * store it */
+ cache = fscache_select_cache_for_object(cookie);
+ if (!cache)
+ goto no_cache; /* couldn't decide on a cache */
+
+ /* create a file index entry on disc, along with all the
+ * indexes required to find it again later */
+ object = fscache_lookup_object(cookie, cache);
+ if (IS_ERR(object)) {
+ ret = PTR_ERR(object);
+ goto error;
+ }
+
+ up_write(&cookie->sem);
+ }
+out:
+ up_read(&fscache_addremove_sem);
+ _leave(" = %p", cookie);
+ return cookie;
+
+no_cache:
+ ret = -ENOMEDIUM;
+ goto error_cleanup;
+error:
+ printk(KERN_ERR "FS-Cache: error from cache: %d\n", ret);
+error_cleanup:
+ if (cookie) {
+ up_write(&cookie->sem);
+ __fscache_cookie_put(cookie);
+ cookie = FSCACHE_NEGATIVE_COOKIE;
+ atomic_dec(&parent->children);
+ }
+
+ goto out;
+
+} /* end __fscache_acquire_cookie() */
+
+EXPORT_SYMBOL(__fscache_acquire_cookie);
+
+/*****************************************************************************/
+/*
+ * release a cookie back to the cache
+ * - the object will be marked as recyclable on disc if retire is true
+ * - all dependents of this cookie must have already been unregistered
+ * (indexes/files/pages)
+ */
+void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
+{
+ struct fscache_cache *cache;
+ struct fscache_object *object;
+ struct hlist_node *_p;
+
+ if (cookie == FSCACHE_NEGATIVE_COOKIE) {
+ _leave(" [no cookie]");
+ return;
+ }
+
+ _enter("%p{%s},%d", cookie, cookie->def->name, retire);
+
+ if (atomic_read(&cookie->children) != 0) {
+ printk("FS-Cache: cookie still has children\n");
+ BUG();
+ }
+
+ /* detach pointers back to the netfs */
+ down_write(&cookie->sem);
+
+ cookie->netfs_data = NULL;
+ cookie->def = NULL;
+
+ /* mark retired objects for recycling */
+ if (retire) {
+ hlist_for_each_entry(object, _p,
+ &cookie->backing_objects,
+ cookie_link
+ ) {
+ set_bit(FSCACHE_OBJECT_RECYCLING, &object->flags);
+ }
+ }
+
+ /* break links with all the active objects */
+ while (!hlist_empty(&cookie->backing_objects)) {
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object,
+ cookie_link);
+
+ /* detach each cache object from the object cookie */
+ set_bit(FSCACHE_OBJECT_RELEASING, &object->flags);
+
+ hlist_del_init(&object->cookie_link);
+
+ cache = object->cache;
+ cache->ops->lock_object(object);
+ object->cookie = NULL;
+ cache->ops->unlock_object(object);
+
+ if (atomic_dec_and_test(&cookie->usage))
+ /* the cookie refcount shouldn't be reduced to 0 yet */
+ BUG();
+
+ spin_lock(&cache->object_list_lock);
+ list_del_init(&object->cache_link);
+ spin_unlock(&cache->object_list_lock);
+
+ cache->ops->put_object(object);
+ }
+
+ up_write(&cookie->sem);
+
+ if (cookie->parent) {
+#ifdef CONFIG_DEBUG_SLAB
+ BUG_ON((atomic_read(&cookie->parent->children) & 0xffff0000) == 0x6b6b0000);
+#endif
+ atomic_dec(&cookie->parent->children);
+ }
+
+ /* finally dispose of the cookie */
+ fscache_cookie_put(cookie);
+
+ _leave("");
+
+} /* end __fscache_relinquish_cookie() */
+
+EXPORT_SYMBOL(__fscache_relinquish_cookie);
+
+/*****************************************************************************/
+/*
+ * update the index entries backing a cookie
+ */
+void __fscache_update_cookie(struct fscache_cookie *cookie)
+{
+ struct fscache_object *object;
+ struct hlist_node *_p;
+
+ if (cookie == FSCACHE_NEGATIVE_COOKIE) {
+ _leave(" [no cookie]");
+ return;
+ }
+
+ _enter("{%s}", cookie->def->name);
+
+ BUG_ON(!cookie->def->get_aux);
+
+ down_write(&cookie->sem);
+ down_read(&cookie->parent->sem);
+
+ /* update the index entry on disc in each cache backing this cookie */
+ hlist_for_each_entry(object, _p,
+ &cookie->backing_objects, cookie_link
+ ) {
+ if (!test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ object->cache->ops->update_object(object);
+ }
+
+ up_read(&cookie->parent->sem);
+ up_write(&cookie->sem);
+ _leave("");
+
+} /* end __fscache_update_cookie() */
+
+EXPORT_SYMBOL(__fscache_update_cookie);
+
+/*****************************************************************************/
+/*
+ * destroy a cookie
+ */
+static void __fscache_cookie_put(struct fscache_cookie *cookie)
+{
+ struct fscache_cookie *parent;
+
+ _enter("%p", cookie);
+
+ for (;;) {
+ parent = cookie->parent;
+ BUG_ON(!hlist_empty(&cookie->backing_objects));
+ kmem_cache_free(fscache_cookie_jar, cookie);
+
+ if (!parent)
+ break;
+
+ cookie = parent;
+ BUG_ON(atomic_read(&cookie->usage) <= 0);
+ if (!atomic_dec_and_test(&cookie->usage))
+ break;
+ }
+
+ _leave("");
+
+} /* end __fscache_cookie_put() */
+
+/*****************************************************************************/
+/*
+ * initialise an cookie jar slab element prior to any use
+ */
+void fscache_cookie_init_once(void *_cookie, kmem_cache_t *cachep,
+ unsigned long flags)
+{
+ struct fscache_cookie *cookie = _cookie;
+
+ if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
+ SLAB_CTOR_CONSTRUCTOR) {
+ memset(cookie, 0, sizeof(*cookie));
+ init_rwsem(&cookie->sem);
+ INIT_HLIST_HEAD(&cookie->backing_objects);
+ }
+
+} /* end fscache_cookie_init_once() */
+
+/*****************************************************************************/
+/*
+ * pin an object into the cache
+ */
+int __fscache_pin_cookie(struct fscache_cookie *cookie)
+{
+ struct fscache_object *object;
+ int ret;
+
+ _enter("%p", cookie);
+
+ if (hlist_empty(&cookie->backing_objects)) {
+ _leave(" = -ENOBUFS");
+ return -ENOBUFS;
+ }
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ /* prevent the file from being uncached whilst we access it and exclude
+ * read and write attempts on pages
+ */
+ down_write(&cookie->sem);
+
+ ret = -ENOBUFS;
+ if (!hlist_empty(&cookie->backing_objects)) {
+ /* get and pin the backing object */
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ goto out;
+
+ if (!object->cache->ops->pin_object) {
+ ret = -EOPNOTSUPP;
+ goto out;
+ }
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ if (object->cache->ops->grab_object(object)) {
+ /* ask the cache to honour the operation */
+ ret = object->cache->ops->pin_object(object);
+
+ object->cache->ops->put_object(object);
+ }
+
+ fscache_operation_unlock(object);
+ }
+ }
+
+out:
+ up_write(&cookie->sem);
+ _leave(" = %d", ret);
+ return ret;
+
+} /* end __fscache_pin_cookie() */
+
+EXPORT_SYMBOL(__fscache_pin_cookie);
+
+/*****************************************************************************/
+/*
+ * unpin an object into the cache
+ */
+void __fscache_unpin_cookie(struct fscache_cookie *cookie)
+{
+ struct fscache_object *object;
+ int ret;
+
+ _enter("%p", cookie);
+
+ if (hlist_empty(&cookie->backing_objects)) {
+ _leave(" [no obj]");
+ return;
+ }
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ /* prevent the file from being uncached whilst we access it and exclude
+ * read and write attempts on pages
+ */
+ down_write(&cookie->sem);
+
+ ret = -ENOBUFS;
+ if (!hlist_empty(&cookie->backing_objects)) {
+ /* get and unpin the backing object */
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ goto out;
+
+ if (!object->cache->ops->unpin_object)
+ goto out;
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ if (object->cache->ops->grab_object(object)) {
+ /* ask the cache to honour the operation */
+ object->cache->ops->unpin_object(object);
+
+ object->cache->ops->put_object(object);
+ }
+
+ fscache_operation_unlock(object);
+ }
+ }
+
+out:
+ up_write(&cookie->sem);
+ _leave("");
+
+} /* end __fscache_unpin_cookie() */
+
+EXPORT_SYMBOL(__fscache_unpin_cookie);
diff --git a/fs/fscache/fscache-int.h b/fs/fscache/fscache-int.h
new file mode 100644
index 0000000..d075660
--- /dev/null
+++ b/fs/fscache/fscache-int.h
@@ -0,0 +1,93 @@
+/* fscache-int.h: internal definitions
+ *
+ * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells at redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifndef _FSCACHE_INT_H
+#define _FSCACHE_INT_H
+
+#include <linux/fscache-cache.h>
+#include <linux/timer.h>
+#include <linux/bio.h>
+
+extern kmem_cache_t *fscache_cookie_jar;
+
+extern struct fscache_cookie fscache_fsdef_index;
+extern struct fscache_cookie_def fscache_fsdef_netfs_def;
+
+extern void fscache_cookie_init_once(void *_cookie, kmem_cache_t *cachep, unsigned long flags);
+
+/*
+ * prevent the cache from being withdrawn whilst an operation is in progress
+ * - returns false if the cache is being withdrawn already or if the cache is
+ * waiting to withdraw itself
+ * - returns true if the cache was not being withdrawn
+ * - fscache_withdraw_cache() will wait using down_write() until all ops are
+ * complete
+ */
+static inline int fscache_operation_lock(struct fscache_object *object)
+{
+ return down_read_trylock(&object->cache->withdrawal_sem);
+}
+
+/*
+ * release the operation lock
+ */
+static inline void fscache_operation_unlock(struct fscache_object *object)
+{
+ up_read(&object->cache->withdrawal_sem);
+}
+
+
+/*****************************************************************************/
+/*
+ * debug tracing
+ */
+#define dbgprintk(FMT,...) \
+ printk("[%-6.6s] "FMT"\n",current->comm ,##__VA_ARGS__)
+#define _dbprintk(FMT,...) do { } while(0)
+
+#define kenter(FMT,...) dbgprintk("==> %s("FMT")",__FUNCTION__ ,##__VA_ARGS__)
+#define kleave(FMT,...) dbgprintk("<== %s()"FMT"",__FUNCTION__ ,##__VA_ARGS__)
+#define kdebug(FMT,...) dbgprintk(FMT ,##__VA_ARGS__)
+
+#define kjournal(FMT,...) _dbprintk(FMT ,##__VA_ARGS__)
+
+#define dbgfree(ADDR) _dbprintk("%p:%d: FREEING %p",__FILE__,__LINE__,ADDR)
+
+#define dbgpgalloc(PAGE) \
+do { \
+ _dbprintk("PGALLOC %s:%d: %p {%lx,%lu}\n", \
+ __FILE__,__LINE__, \
+ (PAGE),(PAGE)->mapping->host->i_ino,(PAGE)->index \
+ ); \
+} while(0)
+
+#define dbgpgfree(PAGE) \
+do { \
+ if ((PAGE)) \
+ _dbprintk("PGFREE %s:%d: %p {%lx,%lu}\n", \
+ __FILE__,__LINE__, \
+ (PAGE), \
+ (PAGE)->mapping->host->i_ino, \
+ (PAGE)->index \
+ ); \
+} while(0)
+
+#ifdef __KDEBUG
+#define _enter(FMT,...) kenter(FMT,##__VA_ARGS__)
+#define _leave(FMT,...) kleave(FMT,##__VA_ARGS__)
+#define _debug(FMT,...) kdebug(FMT,##__VA_ARGS__)
+#else
+#define _enter(FMT,...) do { } while(0)
+#define _leave(FMT,...) do { } while(0)
+#define _debug(FMT,...) do { } while(0)
+#endif
+
+#endif /* _FSCACHE_INT_H */
diff --git a/fs/fscache/fsdef.c b/fs/fscache/fsdef.c
new file mode 100644
index 0000000..75a0d45
--- /dev/null
+++ b/fs/fscache/fsdef.c
@@ -0,0 +1,113 @@
+/* fsdef.c: filesystem index definition
+ *
+ * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells at redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include "fscache-int.h"
+
+static uint16_t fscache_fsdef_netfs_get_key(const void *cookie_netfs_data,
+ void *buffer, uint16_t bufmax);
+
+static uint16_t fscache_fsdef_netfs_get_aux(const void *cookie_netfs_data,
+ void *buffer, uint16_t bufmax);
+
+static fscache_checkaux_t fscache_fsdef_netfs_check_aux(void *cookie_netfs_data,
+ const void *data,
+ uint16_t datalen);
+
+struct fscache_cookie_def fscache_fsdef_netfs_def = {
+ .name = "FSDEF.netfs",
+ .type = FSCACHE_COOKIE_TYPE_INDEX,
+ .get_key = fscache_fsdef_netfs_get_key,
+ .get_aux = fscache_fsdef_netfs_get_aux,
+ .check_aux = fscache_fsdef_netfs_check_aux,
+};
+
+struct fscache_cookie fscache_fsdef_index = {
+ .usage = ATOMIC_INIT(1),
+ .def = NULL,
+ .sem = __RWSEM_INITIALIZER(fscache_fsdef_index.sem),
+ .backing_objects = HLIST_HEAD_INIT,
+};
+
+EXPORT_SYMBOL(fscache_fsdef_index);
+
+/*****************************************************************************/
+/*
+ * get the key data for an FSDEF index record
+ */
+static uint16_t fscache_fsdef_netfs_get_key(const void *cookie_netfs_data,
+ void *buffer, uint16_t bufmax)
+{
+ const struct fscache_netfs *netfs = cookie_netfs_data;
+ unsigned klen;
+
+ _enter("{%s.%u},", netfs->name, netfs->version);
+
+ klen = strlen(netfs->name);
+ if (klen > bufmax)
+ return 0;
+
+ memcpy(buffer, netfs->name, klen);
+ return klen;
+
+} /* end fscache_fsdef_netfs_get_key() */
+
+/*****************************************************************************/
+/*
+ * get the auxilliary data for an FSDEF index record
+ */
+static uint16_t fscache_fsdef_netfs_get_aux(const void *cookie_netfs_data,
+ void *buffer, uint16_t bufmax)
+{
+ const struct fscache_netfs *netfs = cookie_netfs_data;
+ unsigned dlen;
+
+ _enter("{%s.%u},", netfs->name, netfs->version);
+
+ dlen = sizeof(uint32_t);
+ if (dlen > bufmax)
+ return 0;
+
+ memcpy(buffer, &netfs->version, dlen);
+ return dlen;
+
+} /* end fscache_fsdef_netfs_get_aux() */
+
+/*****************************************************************************/
+/*
+ * check that the version stored in the auxilliary data is correct
+ */
+static fscache_checkaux_t fscache_fsdef_netfs_check_aux(void *cookie_netfs_data,
+ const void *data,
+ uint16_t datalen)
+{
+ struct fscache_netfs *netfs = cookie_netfs_data;
+ uint32_t version;
+
+ _enter("{%s},,%hu", netfs->name, datalen);
+
+ if (datalen != sizeof(version)) {
+ _leave(" = OBSOLETE [dl=%d v=%d]",
+ datalen, sizeof(version));
+ return FSCACHE_CHECKAUX_OBSOLETE;
+ }
+
+ memcpy(&version, data, sizeof(version));
+ if (version != netfs->version) {
+ _leave(" = OBSOLETE [ver=%x net=%x]",
+ version, netfs->version);
+ return FSCACHE_CHECKAUX_OBSOLETE;
+ }
+
+ _leave(" = OKAY");
+ return FSCACHE_CHECKAUX_OKAY;
+
+} /* end fscache_fsdef_netfs_check_aux() */
diff --git a/fs/fscache/main.c b/fs/fscache/main.c
new file mode 100644
index 0000000..4697917
--- /dev/null
+++ b/fs/fscache/main.c
@@ -0,0 +1,105 @@
+/* main.c: general filesystem caching manager
+ *
+ * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells at redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/completion.h>
+#include <linux/slab.h>
+#include "fscache-int.h"
+
+int fscache_debug;
+
+static int fscache_init(void);
+static void fscache_exit(void);
+
+fs_initcall(fscache_init);
+module_exit(fscache_exit);
+
+MODULE_DESCRIPTION("FS Cache Manager");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+static void fscache_ktype_release(struct kobject *kobject);
+
+static struct sysfs_ops fscache_sysfs_ops = {
+ .show = NULL,
+ .store = NULL,
+};
+
+static struct kobj_type fscache_ktype = {
+ .release = fscache_ktype_release,
+ .sysfs_ops = &fscache_sysfs_ops,
+ .default_attrs = NULL,
+};
+
+struct kset fscache_kset = {
+ .kobj.name = "fscache",
+ .kobj.kset = &fs_subsys.kset,
+ .ktype = &fscache_ktype,
+};
+
+EXPORT_SYMBOL(fscache_kset);
+
+/*****************************************************************************/
+/*
+ * initialise the fs caching module
+ */
+static int __init fscache_init(void)
+{
+ int ret;
+
+ fscache_cookie_jar =
+ kmem_cache_create("fscache_cookie_jar",
+ sizeof(struct fscache_cookie),
+ 0,
+ 0,
+ fscache_cookie_init_once,
+ NULL);
+
+ if (!fscache_cookie_jar) {
+ printk(KERN_NOTICE
+ "FS-Cache: Failed to allocate a cookie jar\n");
+ return -ENOMEM;
+ }
+
+ ret = kset_register(&fscache_kset);
+ if (ret < 0) {
+ kmem_cache_destroy(fscache_cookie_jar);
+ return ret;
+ }
+
+ printk(KERN_NOTICE "FS-Cache: Loaded\n");
+ return 0;
+
+} /* end fscache_init() */
+
+/*****************************************************************************/
+/*
+ * clean up on module removal
+ */
+static void __exit fscache_exit(void)
+{
+ _enter("");
+
+ kset_unregister(&fscache_kset);
+ kmem_cache_destroy(fscache_cookie_jar);
+ printk(KERN_NOTICE "FS-Cache: unloaded\n");
+
+} /* end fscache_exit() */
+
+/*****************************************************************************/
+/*
+ * release the ktype
+ */
+static void fscache_ktype_release(struct kobject *kobject)
+{
+} /* end fscache_ktype_release() */
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
new file mode 100644
index 0000000..fb5cba0
--- /dev/null
+++ b/fs/fscache/page.c
@@ -0,0 +1,548 @@
+/* page.c: general filesystem cache cookie management
+ *
+ * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells at redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/fscache-cache.h>
+#include <linux/buffer_head.h>
+#include <linux/pagevec.h>
+#include "fscache-int.h"
+
+/*****************************************************************************/
+/*
+ * set the data file size on an object in the cache
+ */
+int __fscache_set_i_size(struct fscache_cookie *cookie, loff_t i_size)
+{
+ struct fscache_object *object;
+ int ret;
+
+ _enter("%p,%llu,", cookie, i_size);
+
+ if (hlist_empty(&cookie->backing_objects)) {
+ _leave(" = -ENOBUFS");
+ return -ENOBUFS;
+ }
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ /* prevent the file from being uncached whilst we access it and exclude
+ * read and write attempts on pages
+ */
+ down_write(&cookie->sem);
+
+ ret = -ENOBUFS;
+ if (!hlist_empty(&cookie->backing_objects)) {
+ /* get and pin the backing object */
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ goto out;
+
+ /* prevent the cache from being withdrawn */
+ if (object->cache->ops->set_i_size &&
+ fscache_operation_lock(object)
+ ) {
+ if (object->cache->ops->grab_object(object)) {
+ /* ask the cache to honour the operation */
+ ret = object->cache->ops->set_i_size(object,
+ i_size);
+
+ object->cache->ops->put_object(object);
+ }
+
+ fscache_operation_unlock(object);
+ }
+ }
+
+out:
+ up_write(&cookie->sem);
+ _leave(" = %d", ret);
+ return ret;
+
+} /* end __fscache_set_i_size() */
+
+EXPORT_SYMBOL(__fscache_set_i_size);
+
+/*****************************************************************************/
+/*
+ * reserve space for an object
+ */
+int __fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
+{
+ struct fscache_object *object;
+ int ret;
+
+ _enter("%p,%llu,", cookie, size);
+
+ if (hlist_empty(&cookie->backing_objects)) {
+ _leave(" = -ENOBUFS");
+ return -ENOBUFS;
+ }
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ /* prevent the file from being uncached whilst we access it and exclude
+ * read and write attempts on pages
+ */
+ down_write(&cookie->sem);
+
+ ret = -ENOBUFS;
+ if (!hlist_empty(&cookie->backing_objects)) {
+ /* get and pin the backing object */
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ goto out;
+
+ if (!object->cache->ops->reserve_space) {
+ ret = -EOPNOTSUPP;
+ goto out;
+ }
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ if (object->cache->ops->grab_object(object)) {
+ /* ask the cache to honour the operation */
+ ret = object->cache->ops->reserve_space(object,
+ size);
+
+ object->cache->ops->put_object(object);
+ }
+
+ fscache_operation_unlock(object);
+ }
+ }
+
+out:
+ up_write(&cookie->sem);
+ _leave(" = %d", ret);
+ return ret;
+
+} /* end __fscache_reserve_space() */
+
+EXPORT_SYMBOL(__fscache_reserve_space);
+
+/*****************************************************************************/
+/*
+ * read a page from the cache or allocate a block in which to store it
+ * - we return:
+ * -ENOMEM - out of memory, nothing done
+ * -EINTR - interrupted
+ * -ENOBUFS - no backing object available in which to cache the block
+ * -ENODATA - no data available in the backing object for this block
+ * 0 - dispatched a read - it'll call end_io_func() when finished
+ */
+int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+{
+ struct fscache_object *object;
+ int ret;
+
+ _enter("%p,{%lu},", cookie, page->index);
+
+ if (hlist_empty(&cookie->backing_objects)) {
+ _leave(" -ENOBUFS [no backing objects]");
+ return -ENOBUFS;
+ }
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ /* prevent the file from being uncached whilst we access it */
+ down_read(&cookie->sem);
+
+ ret = -ENOBUFS;
+ if (!hlist_empty(&cookie->backing_objects)) {
+ /* get and pin the backing object */
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ goto out;
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ if (object->cache->ops->grab_object(object)) {
+ /* ask the cache to honour the operation */
+ ret = object->cache->ops->read_or_alloc_page(
+ object,
+ page,
+ end_io_func,
+ end_io_data,
+ gfp);
+
+ object->cache->ops->put_object(object);
+ }
+
+ fscache_operation_unlock(object);
+ }
+ }
+
+out:
+ up_read(&cookie->sem);
+ _leave(" = %d", ret);
+ return ret;
+
+} /* end __fscache_read_or_alloc_page() */
+
+EXPORT_SYMBOL(__fscache_read_or_alloc_page);
+
+/*****************************************************************************/
+/*
+ * read a list of page from the cache or allocate a block in which to store
+ * them
+ * - we return:
+ * -ENOMEM - out of memory, some pages may be being read
+ * -EINTR - interrupted, some pages may be being read
+ * -ENOBUFS - no backing object or space available in which to cache any
+ * pages not being read
+ * -ENODATA - no data available in the backing object for some or all of
+ * the pages
+ * 0 - dispatched a read on all pages
+ *
+ * end_io_func() will be called for each page read from the cache as it is
+ * finishes being read
+ *
+ * any pages for which a read is dispatched will be removed from pages and
+ * nr_pages
+ */
+int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
+ struct address_space *mapping,
+ struct list_head *pages,
+ unsigned *nr_pages,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+{
+ struct fscache_object *object;
+ int ret;
+
+ _enter("%p,,%d,,,", cookie, *nr_pages);
+
+ if (hlist_empty(&cookie->backing_objects)) {
+ _leave(" -ENOBUFS [no backing objects]");
+ return -ENOBUFS;
+ }
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+ BUG_ON(list_empty(pages));
+ BUG_ON(*nr_pages <= 0);
+
+ /* prevent the file from being uncached whilst we access it */
+ down_read(&cookie->sem);
+
+ ret = -ENOBUFS;
+ if (!hlist_empty(&cookie->backing_objects)) {
+ /* get and pin the backing object */
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ goto out;
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ if (object->cache->ops->grab_object(object)) {
+ /* ask the cache to honour the operation */
+ ret = object->cache->ops->read_or_alloc_pages(
+ object,
+ mapping,
+ pages,
+ nr_pages,
+ end_io_func,
+ end_io_data,
+ gfp);
+
+ object->cache->ops->put_object(object);
+ }
+
+ fscache_operation_unlock(object);
+ }
+ }
+
+out:
+ up_read(&cookie->sem);
+ _leave(" = %d", ret);
+ return ret;
+
+} /* end __fscache_read_or_alloc_pages() */
+
+EXPORT_SYMBOL(__fscache_read_or_alloc_pages);
+
+/*****************************************************************************/
+/*
+ * allocate a block in the cache on which to store a page
+ * - we return:
+ * -ENOMEM - out of memory, nothing done
+ * -EINTR - interrupted
+ * -ENOBUFS - no backing object available in which to cache the block
+ * 0 - block allocated
+ */
+int __fscache_alloc_page(struct fscache_cookie *cookie,
+ struct page *page,
+ gfp_t gfp)
+{
+ struct fscache_object *object;
+ int ret;
+
+ _enter("%p,{%lu},", cookie, page->index);
+
+ if (hlist_empty(&cookie->backing_objects)) {
+ _leave(" -ENOBUFS [no backing objects]");
+ return -ENOBUFS;
+ }
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ /* prevent the file from being uncached whilst we access it */
+ down_read(&cookie->sem);
+
+ ret = -ENOBUFS;
+ if (!hlist_empty(&cookie->backing_objects)) {
+ /* get and pin the backing object */
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ goto out;
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ if (object->cache->ops->grab_object(object)) {
+ /* ask the cache to honour the operation */
+ ret = object->cache->ops->allocate_page(object,
+ page,
+ gfp);
+
+ object->cache->ops->put_object(object);
+ }
+
+ fscache_operation_unlock(object);
+ }
+ }
+
+out:
+ up_read(&cookie->sem);
+ _leave(" = %d", ret);
+ return ret;
+
+} /* end __fscache_alloc_page() */
+
+EXPORT_SYMBOL(__fscache_alloc_page);
+
+/*****************************************************************************/
+/*
+ * request a page be stored in the cache
+ * - returns:
+ * -ENOMEM - out of memory, nothing done
+ * -EINTR - interrupted
+ * -ENOBUFS - no backing object available in which to cache the page
+ * 0 - dispatched a write - it'll call end_io_func() when finished
+ */
+int __fscache_write_page(struct fscache_cookie *cookie,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+{
+ struct fscache_object *object;
+ int ret;
+
+ _enter("%p,{%lu},", cookie, page->index);
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ /* prevent the file from been uncached whilst we deal with it */
+ down_read(&cookie->sem);
+
+ ret = -ENOBUFS;
+ if (!hlist_empty(&cookie->backing_objects)) {
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ goto out;
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ /* ask the cache to honour the operation */
+ ret = object->cache->ops->write_page(object,
+ page,
+ end_io_func,
+ end_io_data,
+ gfp);
+ fscache_operation_unlock(object);
+ }
+ }
+
+out:
+ up_read(&cookie->sem);
+ _leave(" = %d", ret);
+ return ret;
+
+} /* end __fscache_write_page() */
+
+EXPORT_SYMBOL(__fscache_write_page);
+
+/*****************************************************************************/
+/*
+ * request several pages be stored in the cache
+ * - returns:
+ * -ENOMEM - out of memory, nothing done
+ * -EINTR - interrupted
+ * -ENOBUFS - no backing object available in which to cache the page
+ * 0 - dispatched a write - it'll call end_io_func() when finished
+ */
+int __fscache_write_pages(struct fscache_cookie *cookie,
+ struct pagevec *pagevec,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+{
+ struct fscache_object *object;
+ int ret;
+
+ _enter("%p,{%ld},", cookie, pagevec->nr);
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ /* prevent the file from been uncached whilst we deal with it */
+ down_read(&cookie->sem);
+
+ ret = -ENOBUFS;
+ if (!hlist_empty(&cookie->backing_objects)) {
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ if (test_bit(FSCACHE_IOERROR, &object->cache->flags))
+ goto out;
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ /* ask the cache to honour the operation */
+ ret = object->cache->ops->write_pages(object,
+ pagevec,
+ end_io_func,
+ end_io_data,
+ gfp);
+ fscache_operation_unlock(object);
+ }
+ }
+
+out:
+ up_read(&cookie->sem);
+ _leave(" = %d", ret);
+ return ret;
+
+} /* end __fscache_write_pages() */
+
+EXPORT_SYMBOL(__fscache_write_pages);
+
+/*****************************************************************************/
+/*
+ * remove a page from the cache
+ */
+void __fscache_uncache_page(struct fscache_cookie *cookie, struct page *page)
+{
+ struct fscache_object *object;
+ struct pagevec pagevec;
+
+ _enter(",{%lu}", page->index);
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ if (hlist_empty(&cookie->backing_objects)) {
+ _leave(" [no backing]");
+ return;
+ }
+
+ pagevec_init(&pagevec, 0);
+ pagevec_add(&pagevec, page);
+
+ /* ask the cache to honour the operation */
+ down_read(&cookie->sem);
+
+ if (!hlist_empty(&cookie->backing_objects)) {
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ object->cache->ops->uncache_pages(object, &pagevec);
+ fscache_operation_unlock(object);
+ }
+ }
+
+ up_read(&cookie->sem);
+
+ _leave("");
+ return;
+
+} /* end __fscache_uncache_page() */
+
+EXPORT_SYMBOL(__fscache_uncache_page);
+
+/*****************************************************************************/
+/*
+ * remove a bunch of pages from the cache
+ */
+void __fscache_uncache_pages(struct fscache_cookie *cookie,
+ struct pagevec *pagevec)
+{
+ struct fscache_object *object;
+
+ _enter(",{%ld}", pagevec->nr);
+
+ BUG_ON(pagevec->nr <= 0);
+ BUG_ON(!pagevec->pages[0]);
+
+ /* not supposed to use this for indexes */
+ BUG_ON(cookie->def->type == FSCACHE_COOKIE_TYPE_INDEX);
+
+ if (hlist_empty(&cookie->backing_objects)) {
+ _leave(" [no backing]");
+ return;
+ }
+
+ /* ask the cache to honour the operation */
+ down_read(&cookie->sem);
+
+ if (!hlist_empty(&cookie->backing_objects)) {
+ object = hlist_entry(cookie->backing_objects.first,
+ struct fscache_object, cookie_link);
+
+ /* prevent the cache from being withdrawn */
+ if (fscache_operation_lock(object)) {
+ object->cache->ops->uncache_pages(object, pagevec);
+ fscache_operation_unlock(object);
+ }
+ }
+
+ up_read(&cookie->sem);
+
+ _leave("");
+ return;
+
+} /* end __fscache_uncache_pages() */
+
+EXPORT_SYMBOL(__fscache_uncache_pages);
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
new file mode 100644
index 0000000..70c0a85
--- /dev/null
+++ b/include/linux/fscache-cache.h
@@ -0,0 +1,226 @@
+/* fscache-cache.h: general filesystem caching backing cache interface
+ *
+ * Copyright (C) 2004-6 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells at redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * NOTE!!! See:
+ *
+ * Documentation/filesystems/caching/backend-api.txt
+ *
+ * for a description of the cache backend interface declared here.
+ */
+
+#ifndef _LINUX_FSCACHE_CACHE_H
+#define _LINUX_FSCACHE_CACHE_H
+
+#include <linux/fscache.h>
+
+#define NR_MAXCACHES BITS_PER_LONG
+
+struct fscache_cache;
+struct fscache_cache_ops;
+struct fscache_object;
+
+/*
+ * cache tag definition
+ */
+struct fscache_cache_tag {
+ struct list_head link;
+ struct fscache_cache *cache; /* cache referred to by this tag */
+ atomic_t usage;
+ char name[0]; /* tag name */
+};
+
+/*
+ * cache definition
+ */
+struct fscache_cache {
+ struct fscache_cache_ops *ops;
+ struct fscache_cache_tag *tag; /* tag representing this cache */
+ struct list_head link; /* link in list of caches */
+ struct rw_semaphore withdrawal_sem; /* withdrawal control sem */
+ size_t max_index_size; /* maximum size of index data */
+ char identifier[32]; /* cache label */
+
+ /* node management */
+ struct list_head object_list; /* list of data/index objects */
+ spinlock_t object_list_lock;
+ struct fscache_object *fsdef; /* object for the fsdef index */
+ unsigned long flags;
+#define FSCACHE_IOERROR 0 /* cache stopped on I/O error */
+};
+
+extern void fscache_init_cache(struct fscache_cache *cache,
+ struct fscache_cache_ops *ops,
+ const char *idfmt,
+ ...) __attribute__ ((format (printf,3,4)));
+
+extern int fscache_add_cache(struct fscache_cache *cache,
+ struct fscache_object *fsdef,
+ const char *tagname);
+extern void fscache_withdraw_cache(struct fscache_cache *cache);
+
+extern void fscache_io_error(struct fscache_cache *cache);
+
+/*****************************************************************************/
+/*
+ * cache operations
+ */
+struct fscache_cache_ops {
+ /* name of cache provider */
+ const char *name;
+
+ /* look up the object for a cookie, creating it on disc if necessary */
+ struct fscache_object *(*lookup_object)(struct fscache_cache *cache,
+ struct fscache_object *parent,
+ struct fscache_cookie *cookie);
+
+ /* increment the usage count on this object (may fail if unmounting) */
+ struct fscache_object *(*grab_object)(struct fscache_object *object);
+
+ /* lock a semaphore on an object */
+ void (*lock_object)(struct fscache_object *object);
+
+ /* unlock a semaphore on an object */
+ void (*unlock_object)(struct fscache_object *object);
+
+ /* pin an object in the cache */
+ int (*pin_object)(struct fscache_object *object);
+
+ /* unpin an object in the cache */
+ void (*unpin_object)(struct fscache_object *object);
+
+ /* store the updated auxilliary data on an object */
+ void (*update_object)(struct fscache_object *object);
+
+ /* dispose of a reference to an object */
+ void (*put_object)(struct fscache_object *object);
+
+ /* sync a cache */
+ void (*sync_cache)(struct fscache_cache *cache);
+
+ /* set the data size of an object */
+ int (*set_i_size)(struct fscache_object *object, loff_t i_size);
+
+ /* reserve space for an object's data and associated metadata */
+ int (*reserve_space)(struct fscache_object *object, loff_t i_size);
+
+ /* request a backing block for a page be read or allocated in the
+ * cache */
+ int (*read_or_alloc_page)(struct fscache_object *object,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ unsigned long gfp);
+
+ /* request backing blocks for a list of pages be read or allocated in
+ * the cache */
+ int (*read_or_alloc_pages)(struct fscache_object *object,
+ struct address_space *mapping,
+ struct list_head *pages,
+ unsigned *nr_pages,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ unsigned long gfp);
+
+ /* request a backing block for a page be allocated in the cache so that
+ * it can be written directly */
+ int (*allocate_page)(struct fscache_object *object,
+ struct page *page,
+ unsigned long gfp);
+
+ /* write a page to its backing block in the cache */
+ int (*write_page)(struct fscache_object *object,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ unsigned long gfp);
+
+ /* write several pages to their backing blocks in the cache */
+ int (*write_pages)(struct fscache_object *object,
+ struct pagevec *pagevec,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ unsigned long gfp);
+
+ /* detach backing block from a bunch of pages */
+ void (*uncache_pages)(struct fscache_object *object,
+ struct pagevec *pagevec);
+
+ /* dissociate a cache from all the pages it was backing */
+ void (*dissociate_pages)(struct fscache_cache *cache);
+};
+
+/*****************************************************************************/
+/*
+ * data file or index object cookie
+ * - a file will only appear in one cache
+ * - a request to cache a file may or may not be honoured, subject to
+ * constraints such as disc space
+ * - indexes files are created on disc just-in-time
+ */
+struct fscache_cookie {
+ atomic_t usage; /* number of users of this cookie */
+ atomic_t children; /* number of children of this cookie */
+ struct rw_semaphore sem; /* list creation vs scan lock */
+ struct hlist_head backing_objects; /* object(s) backing this file/index */
+ struct fscache_cookie_def *def; /* definition */
+ struct fscache_cookie *parent; /* parent of this entry */
+ struct fscache_netfs *netfs; /* owner network fs definition */
+ void *netfs_data; /* back pointer to netfs */
+};
+
+extern struct fscache_cookie fscache_fsdef_index;
+
+/*****************************************************************************/
+/*
+ * on-disc cache file or index handle
+ */
+struct fscache_object {
+ unsigned long flags;
+#define FSCACHE_OBJECT_RELEASING 0 /* T if object is being released */
+#define FSCACHE_OBJECT_RECYCLING 1 /* T if object is being retired */
+#define FSCACHE_OBJECT_WITHDRAWN 2 /* T if object has been withdrawn */
+
+ struct list_head cache_link; /* link in cache->object_list */
+ struct hlist_node cookie_link; /* link in cookie->backing_objects */
+ struct fscache_cache *cache; /* cache that supplied this object */
+ struct fscache_cookie *cookie; /* netfs's file/index object */
+};
+
+static inline
+void fscache_object_init(struct fscache_object *object)
+{
+ object->flags = 0;
+ INIT_LIST_HEAD(&object->cache_link);
+ INIT_HLIST_NODE(&object->cookie_link);
+ object->cache = NULL;
+ object->cookie = NULL;
+}
+
+/* find the parent index object for a object */
+static inline
+struct fscache_object *fscache_find_parent_object(struct fscache_object *object)
+{
+ struct fscache_object *parent;
+ struct fscache_cookie *cookie = object->cookie;
+ struct fscache_cache *cache = object->cache;
+ struct hlist_node *_p;
+
+ hlist_for_each_entry(parent, _p,
+ &cookie->parent->backing_objects,
+ cookie_link
+ ) {
+ if (parent->cache == cache)
+ return parent;
+ }
+
+ return NULL;
+}
+
+#endif /* _LINUX_FSCACHE_CACHE_H */
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
new file mode 100644
index 0000000..50141b9
--- /dev/null
+++ b/include/linux/fscache.h
@@ -0,0 +1,486 @@
+/* fscache.h: general filesystem caching interface
+ *
+ * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells at redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * NOTE!!! See:
+ *
+ * Documentation/filesystems/caching/netfs-api.txt
+ *
+ * for a description of the network filesystem interface declared here.
+ */
+
+#ifndef _LINUX_FSCACHE_H
+#define _LINUX_FSCACHE_H
+
+#include <linux/config.h>
+#include <linux/fs.h>
+#include <linux/list.h>
+#include <linux/pagemap.h>
+#include <linux/pagevec.h>
+
+struct pagevec;
+struct fscache_cache_tag;
+struct fscache_cookie;
+struct fscache_netfs;
+struct fscache_netfs_operations;
+
+#define FSCACHE_NEGATIVE_COOKIE ((struct fscache_cookie *) NULL)
+
+typedef void (*fscache_rw_complete_t)(struct page *page,
+ void *data,
+ int error);
+
+/* result of index entry consultation */
+typedef enum {
+ FSCACHE_CHECKAUX_OKAY, /* entry okay as is */
+ FSCACHE_CHECKAUX_NEEDS_UPDATE, /* entry requires update */
+ FSCACHE_CHECKAUX_OBSOLETE, /* entry requires deletion */
+} fscache_checkaux_t;
+
+/*****************************************************************************/
+/*
+ * fscache cookie definition
+ */
+struct fscache_cookie_def
+{
+ /* name of cookie type */
+ char name[16];
+
+ /* cookie type */
+ uint8_t type;
+#define FSCACHE_COOKIE_TYPE_INDEX 0
+#define FSCACHE_COOKIE_TYPE_DATAFILE 1
+
+ /* select the cache into which to insert an entry in this index
+ * - optional
+ * - should return a cache identifier or NULL to cause the cache to be
+ * inherited from the parent if possible or the first cache picked
+ * for a non-index file if not
+ */
+ struct fscache_cache_tag *(*select_cache)(const void *parent_netfs_data,
+ const void *cookie_netfs_data);
+
+ /* get an index key
+ * - should store the key data in the buffer
+ * - should return the amount of amount stored
+ * - not permitted to return an error
+ * - the netfs data from the cookie being used as the source is
+ * presented
+ */
+ uint16_t (*get_key)(const void *cookie_netfs_data,
+ void *buffer,
+ uint16_t bufmax);
+
+ /* get certain file attributes from the netfs data
+ * - this function can be absent for an index
+ * - not permitted to return an error
+ * - the netfs data from the cookie being used as the source is
+ * presented
+ */
+ void (*get_attr)(const void *cookie_netfs_data, uint64_t *size);
+
+ /* get the auxilliary data from netfs data
+ * - this function can be absent if the index carries no state data
+ * - should store the auxilliary data in the buffer
+ * - should return the amount of amount stored
+ * - not permitted to return an error
+ * - the netfs data from the cookie being used as the source is
+ * presented
+ */
+ uint16_t (*get_aux)(const void *cookie_netfs_data,
+ void *buffer,
+ uint16_t bufmax);
+
+ /* consult the netfs about the state of an object
+ * - this function can be absent if the index carries no state data
+ * - the netfs data from the cookie being used as the target is
+ * presented, as is the auxilliary data
+ */
+ fscache_checkaux_t (*check_aux)(void *cookie_netfs_data,
+ const void *data,
+ uint16_t datalen);
+
+ /* indicate pages that now have cache metadata retained
+ * - this function should mark the specified pages as now being cached
+ */
+ void (*mark_pages_cached)(void *cookie_netfs_data,
+ struct address_space *mapping,
+ struct pagevec *cached_pvec);
+
+ /* indicate the cookie is no longer uncached
+ * - this function is called when the backing store currently caching
+ * a cookie is removed
+ * - the netfs should use this to clean up any markers indicating
+ * cached pages
+ * - this is mandatory for any object that may have data
+ */
+ void (*now_uncached)(void *cookie_netfs_data);
+};
+
+/* pattern used to fill dead space in an index entry */
+#define FSCACHE_INDEX_DEADFILL_PATTERN 0x79
+
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern struct fscache_cookie *__fscache_acquire_cookie(struct fscache_cookie *parent,
+ struct fscache_cookie_def *def,
+ void *netfs_data);
+
+extern void __fscache_relinquish_cookie(struct fscache_cookie *cookie,
+ int retire);
+
+extern void __fscache_update_cookie(struct fscache_cookie *cookie);
+#endif
+
+static inline
+struct fscache_cookie *fscache_acquire_cookie(struct fscache_cookie *parent,
+ struct fscache_cookie_def *def,
+ void *netfs_data)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (parent != FSCACHE_NEGATIVE_COOKIE)
+ return __fscache_acquire_cookie(parent, def, netfs_data);
+#endif
+ return FSCACHE_NEGATIVE_COOKIE;
+}
+
+static inline
+void fscache_relinquish_cookie(struct fscache_cookie *cookie,
+ int retire)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ __fscache_relinquish_cookie(cookie, retire);
+#endif
+}
+
+static inline
+void fscache_update_cookie(struct fscache_cookie *cookie)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ __fscache_update_cookie(cookie);
+#endif
+}
+
+/*****************************************************************************/
+/*
+ * pin or unpin a cookie in a cache
+ * - only available for data cookies
+ */
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern int __fscache_pin_cookie(struct fscache_cookie *cookie);
+extern void __fscache_unpin_cookie(struct fscache_cookie *cookie);
+#endif
+
+static inline
+int fscache_pin_cookie(struct fscache_cookie *cookie)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ return __fscache_pin_cookie(cookie);
+#endif
+ return -ENOBUFS;
+}
+
+static inline
+void fscache_unpin_cookie(struct fscache_cookie *cookie)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ __fscache_unpin_cookie(cookie);
+#endif
+}
+
+/*****************************************************************************/
+/*
+ * fscache cached network filesystem type
+ * - name, version and ops must be filled in before registration
+ * - all other fields will be set during registration
+ */
+struct fscache_netfs
+{
+ uint32_t version; /* indexing version */
+ const char *name; /* filesystem name */
+ struct fscache_cookie *primary_index;
+ struct fscache_netfs_operations *ops;
+ struct list_head link; /* internal link */
+};
+
+struct fscache_netfs_operations
+{
+};
+
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern int __fscache_register_netfs(struct fscache_netfs *netfs);
+extern void __fscache_unregister_netfs(struct fscache_netfs *netfs);
+#endif
+
+static inline
+int fscache_register_netfs(struct fscache_netfs *netfs)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ return __fscache_register_netfs(netfs);
+#else
+ return 0;
+#endif
+}
+
+static inline
+void fscache_unregister_netfs(struct fscache_netfs *netfs)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ __fscache_unregister_netfs(netfs);
+#endif
+}
+
+/*****************************************************************************/
+/*
+ * look up a cache tag
+ * - cache tags are used to select specific caches in which to cache indexes
+ */
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *name);
+extern void __fscache_release_cache_tag(struct fscache_cache_tag *tag);
+#endif
+
+static inline
+struct fscache_cache_tag *fscache_lookup_cache_tag(const char *name)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ return __fscache_lookup_cache_tag(name);
+#else
+ return NULL;
+#endif
+}
+
+static inline
+void fscache_release_cache_tag(struct fscache_cache_tag *tag)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ __fscache_release_cache_tag(tag);
+#endif
+}
+
+/*****************************************************************************/
+/*
+ * set the data size on a cached object
+ * - no pages beyond the end of the object will be accessible
+ * - returns -ENOBUFS if the file is not backed
+ * - returns -ENOSPC if a pinned file of that size can't be stored
+ * - returns 0 if okay
+ */
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern int __fscache_set_i_size(struct fscache_cookie *cookie, loff_t i_size);
+#endif
+
+static inline
+int fscache_set_i_size(struct fscache_cookie *cookie, loff_t i_size)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ return __fscache_set_i_size(cookie, i_size);
+#endif
+ return -ENOBUFS;
+}
+
+/*****************************************************************************/
+/*
+ * reserve data space for a cached object
+ * - returns -ENOBUFS if the file is not backed
+ * - returns -ENOSPC if there isn't enough space to honour the reservation
+ * - returns 0 if okay
+ */
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern int __fscache_reserve_space(struct fscache_cookie *cookie, loff_t size);
+#endif
+
+static inline
+int fscache_reserve_space(struct fscache_cookie *cookie, loff_t size)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ return __fscache_reserve_space(cookie, size);
+#endif
+ return -ENOBUFS;
+}
+
+/*****************************************************************************/
+/*
+ * read a page from the cache or allocate a block in which to store it
+ * - if the page is not backed by a file:
+ * - -ENOBUFS will be returned and nothing more will be done
+ * - else if the page is backed by a block in the cache:
+ * - a read will be started which will call end_io_func on completion
+ * - else if the page is unbacked:
+ * - a block will be allocated
+ * - -ENODATA will be returned
+ */
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp);
+#endif
+
+static inline
+int fscache_read_or_alloc_page(struct fscache_cookie *cookie,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ return __fscache_read_or_alloc_page(cookie, page, end_io_func,
+ end_io_data, gfp);
+#endif
+ return -ENOBUFS;
+}
+
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
+ struct address_space *mapping,
+ struct list_head *pages,
+ unsigned *nr_pages,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp);
+#endif
+
+static inline
+int fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
+ struct address_space *mapping,
+ struct list_head *pages,
+ unsigned *nr_pages,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ return __fscache_read_or_alloc_pages(cookie, mapping, pages,
+ nr_pages, end_io_func,
+ end_io_data, gfp);
+#endif
+ return -ENOBUFS;
+}
+
+/*
+ * allocate a block in which to store a page
+ * - if the page is not backed by a file:
+ * - -ENOBUFS will be returned and nothing more will be done
+ * - else
+ * - a block will be allocated if there isn't one
+ * - 0 will be returned
+ */
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern int __fscache_alloc_page(struct fscache_cookie *cookie,
+ struct page *page,
+ gfp_t gfp);
+#endif
+
+static inline
+int fscache_alloc_page(struct fscache_cookie *cookie,
+ struct page *page,
+ gfp_t gfp)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ return __fscache_alloc_page(cookie, page, gfp);
+#endif
+ return -ENOBUFS;
+}
+
+/*
+ * request a page be stored in the cache
+ * - this request may be ignored if no cache block is currently allocated, in
+ * which case it:
+ * - returns -ENOBUFS
+ * - if a cache block was already allocated:
+ * - a BIO will be dispatched to write the page (end_io_func will be called
+ * from the completion function)
+ * - returns 0
+ */
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern int __fscache_write_page(struct fscache_cookie *cookie,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp);
+
+extern int __fscache_write_pages(struct fscache_cookie *cookie,
+ struct pagevec *pagevec,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp);
+#endif
+
+static inline
+int fscache_write_page(struct fscache_cookie *cookie,
+ struct page *page,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ return __fscache_write_page(cookie, page, end_io_func,
+ end_io_data, gfp);
+#endif
+ return -ENOBUFS;
+}
+
+static inline
+int fscache_write_pages(struct fscache_cookie *cookie,
+ struct pagevec *pagevec,
+ fscache_rw_complete_t end_io_func,
+ void *end_io_data,
+ gfp_t gfp)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ return __fscache_write_pages(cookie, pagevec, end_io_func,
+ end_io_data, gfp);
+#endif
+ return -ENOBUFS;
+}
+
+/*
+ * indicate that caching is no longer required on a page
+ * - note: cannot cancel any outstanding BIOs between this page and the cache
+ */
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+extern void __fscache_uncache_page(struct fscache_cookie *cookie,
+ struct page *page);
+extern void __fscache_uncache_pages(struct fscache_cookie *cookie,
+ struct pagevec *pagevec);
+#endif
+
+static inline
+void fscache_uncache_page(struct fscache_cookie *cookie,
+ struct page *page)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ __fscache_uncache_page(cookie, page);
+#endif
+}
+
+static inline
+void fscache_uncache_pagevec(struct fscache_cookie *cookie,
+ struct pagevec *pagevec)
+{
+#if defined(CONFIG_FSCACHE) || defined(CONFIG_FSCACHE_MODULE)
+ if (cookie != FSCACHE_NEGATIVE_COOKIE)
+ __fscache_uncache_pages(cookie, pagevec);
+#endif
+}
+
+#endif /* _LINUX_FSCACHE_H */
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