[dm-devel] [PATCH 2/5] dm core: enable request-based dm
Kiyoshi Ueda
k-ueda at ct.jp.nec.com
Tue Jun 2 07:01:00 UTC 2009
This patch enables request-based dm.
o Request-based dm and bio-based dm coexist, since there are
some target drivers which are more fitting to bio-based dm.
Also, there are other bio-based devices in the kernel
(e.g. md, loop).
Since bio-based device can't receive struct request,
there are some limitations on device stacking between
bio-based and request-based.
type of underlying device
bio-based requeset-based
----------------------------------------------
bio-based OK OK
request-based NG OK
The device type is recognized by the queue flag in the kernel,
so dm follows that.
o The type of a dm device is decided at the first table binding time.
Once the type of a dm device is decided, the type can't be changed.
o Mempool allocations are deferred to at the table loading time, since
mempools for request-based dm are different from those for bio-based
dm and needed mempool type is fixed by the type of table.
o Currently, request-based dm supports only tables that have a single
target. To support multiple targets, we need to support request
splitting or prevent bio/request from spanning multiple targets.
The former needs lots of changes in the block layer, and the latter
needs that all target drivers support merge() function.
Both will take a time.
Signed-off-by: Kiyoshi Ueda <k-ueda at ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura at ce.jp.nec.com>
Cc: Alasdair G Kergon <agk at redhat.com>
---
drivers/md/dm-ioctl.c | 13 ++++
drivers/md/dm-table.c | 111 ++++++++++++++++++++++++++++++++++
drivers/md/dm.c | 162 +++++++++++++++++++++++++++++++++++++++++---------
drivers/md/dm.h | 25 +++++++
4 files changed, 285 insertions(+), 26 deletions(-)
Index: linux-2.6-block/drivers/md/dm-table.c
===================================================================
--- linux-2.6-block.orig/drivers/md/dm-table.c
+++ linux-2.6-block/drivers/md/dm-table.c
@@ -41,6 +41,7 @@
struct dm_table {
struct mapped_device *md;
atomic_t holders;
+ unsigned type;
/* btree table */
unsigned int depth;
@@ -71,6 +72,8 @@ struct dm_table {
/* events get handed up using this callback */
void (*event_fn)(void *);
void *event_context;
+
+ struct dm_md_mempools *mempools;
};
/*
@@ -264,6 +267,8 @@ void dm_table_destroy(struct dm_table *t
if (t->devices.next != &t->devices)
free_devices(&t->devices);
+ dm_free_md_mempools(t->mempools);
+
kfree(t);
}
@@ -794,6 +799,99 @@ int dm_table_add_target(struct dm_table
return r;
}
+int dm_table_set_type(struct dm_table *t)
+{
+ unsigned i;
+ unsigned bio_based = 0, request_based = 0;
+ struct dm_target *tgt;
+ struct dm_dev_internal *dd;
+ struct list_head *devices;
+
+ for (i = 0; i < t->num_targets; i++) {
+ tgt = t->targets + i;
+ if (dm_target_request_based(tgt))
+ request_based = 1;
+ else
+ bio_based = 1;
+
+ if (bio_based && request_based) {
+ DMWARN("Inconsistent table: different target types"
+ " can't be mixed up");
+ return -EINVAL;
+ }
+ }
+
+ if (bio_based) {
+ /* We must use this table as bio-based */
+ t->type = DM_TYPE_BIO_BASED;
+ return 0;
+ }
+
+ BUG_ON(!request_based); /* No targets in this table */
+
+ /* Non-request-stackable devices can't be used for request-based dm */
+ devices = dm_table_get_devices(t);
+ list_for_each_entry(dd, devices, list) {
+ if (!blk_queue_stackable(bdev_get_queue(dd->dm_dev.bdev))) {
+ DMWARN("table load rejected: including"
+ " non-request-stackable devices");
+ return -EINVAL;
+ }
+ }
+
+ /*
+ * Request-based dm supports only tables that have a single target now.
+ * To support multiple targets, request splitting support is needed,
+ * and that needs lots of changes in the block-layer.
+ * (e.g. request completion process for partial completion.)
+ */
+ if (t->num_targets > 1) {
+ DMWARN("Request-based dm doesn't support multiple targets yet");
+ return -EINVAL;
+ }
+
+ t->type = DM_TYPE_REQUEST_BASED;
+
+ return 0;
+}
+
+unsigned dm_table_get_type(struct dm_table *t)
+{
+ return t->type;
+}
+
+bool dm_table_request_based(struct dm_table *t)
+{
+ return dm_table_get_type(t) == DM_TYPE_REQUEST_BASED;
+}
+
+int dm_table_alloc_md_mempools(struct dm_table *t)
+{
+ unsigned type = dm_table_get_type(t);
+
+ if (unlikely(type == DM_TYPE_NONE)) {
+ DMWARN("no table type is set, can't allocate mempools");
+ return -EINVAL;
+ }
+
+ t->mempools = dm_alloc_md_mempools(type);
+ if (!t->mempools)
+ return -ENOMEM;
+
+ return 0;
+}
+
+void dm_table_free_md_mempools(struct dm_table *t)
+{
+ dm_free_md_mempools(t->mempools);
+ t->mempools = NULL;
+}
+
+struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t)
+{
+ return t->mempools;
+}
+
static int setup_indexes(struct dm_table *t)
{
int i;
@@ -972,6 +1070,19 @@ void dm_table_set_restrictions(struct dm
queue_flag_set_unlocked(QUEUE_FLAG_CLUSTER, q);
dm_table_set_integrity(t);
+
+ /*
+ * QUEUE_FLAG_STACKABLE must be set after all queue settings are
+ * visible to other CPUs because, once the flag is set, incoming bios
+ * are processed by request-based dm, which refers to the queue
+ * settings.
+ * Until the flag set, bios are passed to bio-based dm and queued to
+ * md->deferred where queue settings are not needed yet.
+ * Those bios are passed to request-based dm at the resume time.
+ */
+ smp_mb();
+ if (dm_table_request_based(t))
+ queue_flag_set_unlocked(QUEUE_FLAG_STACKABLE, q);
}
unsigned int dm_table_get_num_targets(struct dm_table *t)
Index: linux-2.6-block/drivers/md/dm.c
===================================================================
--- linux-2.6-block.orig/drivers/md/dm.c
+++ linux-2.6-block/drivers/md/dm.c
@@ -185,6 +185,15 @@ struct mapped_device {
struct bio barrier_bio;
};
+/*
+ * For mempools pre-allocation at the table loading time.
+ */
+struct dm_md_mempools {
+ mempool_t *io_pool;
+ mempool_t *tio_pool;
+ struct bio_set *bs;
+};
+
#define MIN_IOS 256
static struct kmem_cache *_io_cache;
static struct kmem_cache *_tio_cache;
@@ -1790,10 +1799,22 @@ static struct mapped_device *alloc_dev(i
INIT_LIST_HEAD(&md->uevent_list);
spin_lock_init(&md->uevent_lock);
- md->queue = blk_alloc_queue(GFP_KERNEL);
+ md->queue = blk_init_queue(dm_request_fn, NULL);
if (!md->queue)
goto bad_queue;
+ /*
+ * Request-based dm devices cannot be stacked on top of bio-based dm
+ * devices. The type of this dm device has not been decided yet,
+ * although we initialized the queue using blk_init_queue().
+ * The type is decided at the first table loading time.
+ * To prevent problematic device stacking, clear the queue flag
+ * for request stacking support until then.
+ *
+ * This queue is new, so no concurrency on the queue_flags.
+ */
+ queue_flag_clear_unlocked(QUEUE_FLAG_STACKABLE, md->queue);
+ md->saved_make_request_fn = md->queue->make_request_fn;
md->queue->queuedata = md;
md->queue->backing_dev_info.congested_fn = dm_any_congested;
md->queue->backing_dev_info.congested_data = md;
@@ -1802,18 +1823,9 @@ static struct mapped_device *alloc_dev(i
blk_queue_bounce_limit(md->queue, BLK_BOUNCE_ANY);
md->queue->unplug_fn = dm_unplug_all;
blk_queue_merge_bvec(md->queue, dm_merge_bvec);
-
- md->io_pool = mempool_create_slab_pool(MIN_IOS, _io_cache);
- if (!md->io_pool)
- goto bad_io_pool;
-
- md->tio_pool = mempool_create_slab_pool(MIN_IOS, _tio_cache);
- if (!md->tio_pool)
- goto bad_tio_pool;
-
- md->bs = bioset_create(16, 0);
- if (!md->bs)
- goto bad_no_bioset;
+ blk_queue_softirq_done(md->queue, dm_softirq_done);
+ blk_queue_prep_rq(md->queue, dm_prep_fn);
+ blk_queue_lld_busy(md->queue, dm_lld_busy);
md->disk = alloc_disk(1);
if (!md->disk)
@@ -1855,12 +1867,6 @@ bad_bdev:
bad_thread:
put_disk(md->disk);
bad_disk:
- bioset_free(md->bs);
-bad_no_bioset:
- mempool_destroy(md->tio_pool);
-bad_tio_pool:
- mempool_destroy(md->io_pool);
-bad_io_pool:
blk_cleanup_queue(md->queue);
bad_queue:
free_minor(minor);
@@ -1880,9 +1886,12 @@ static void free_dev(struct mapped_devic
unlock_fs(md);
bdput(md->bdev);
destroy_workqueue(md->wq);
- mempool_destroy(md->tio_pool);
- mempool_destroy(md->io_pool);
- bioset_free(md->bs);
+ if (md->tio_pool)
+ mempool_destroy(md->tio_pool);
+ if (md->io_pool)
+ mempool_destroy(md->io_pool);
+ if (md->bs)
+ bioset_free(md->bs);
blk_integrity_unregister(md->disk);
del_gendisk(md->disk);
free_minor(minor);
@@ -1897,6 +1906,29 @@ static void free_dev(struct mapped_devic
kfree(md);
}
+static void __bind_mempools(struct mapped_device *md, struct dm_table *t)
+{
+ struct dm_md_mempools *p;
+
+ if (md->io_pool && md->tio_pool && md->bs)
+ /* the md already has necessary mempools */
+ goto out;
+
+ p = dm_table_get_md_mempools(t);
+ BUG_ON(!p || md->io_pool || md->tio_pool || md->bs);
+
+ md->io_pool = p->io_pool;
+ p->io_pool = NULL;
+ md->tio_pool = p->tio_pool;
+ p->tio_pool = NULL;
+ md->bs = p->bs;
+ p->bs = NULL;
+
+out:
+ /* mempool bind completed, now no need any mempools in the table */
+ dm_table_free_md_mempools(t);
+}
+
/*
* Bind a table to the device.
*/
@@ -1947,6 +1979,18 @@ static int __bind(struct mapped_device *
dm_table_event_callback(t, event_callback, md);
+ /*
+ * The queue hasn't been stopped yet, if the old table type wasn't
+ * for request-based during suspension. So stop it to prevent
+ * I/O mapping before resume.
+ * This must be done before setting the queue restrictions,
+ * because request-based dm may be run just after the setting.
+ */
+ if (dm_table_request_based(t) && !blk_queue_stopped(q))
+ stop_queue(q);
+
+ __bind_mempools(md, t);
+
write_lock(&md->map_lock);
md->map = t;
dm_table_set_restrictions(t, q);
@@ -2160,10 +2204,14 @@ static void dm_wq_work(struct work_struc
up_write(&md->io_lock);
- if (bio_barrier(c))
- process_barrier(md, c);
- else
- __split_and_process_bio(md, c);
+ if (dm_request_based(md))
+ generic_make_request(c);
+ else {
+ if (bio_barrier(c))
+ process_barrier(md, c);
+ else
+ __split_and_process_bio(md, c);
+ }
down_write(&md->io_lock);
}
@@ -2191,6 +2239,13 @@ int dm_swap_table(struct mapped_device *
if (!dm_suspended(md))
goto out;
+ /* cannot change the device type, once a table is bound */
+ if (md->map &&
+ (dm_table_get_type(md->map) != dm_table_get_type(table))) {
+ DMWARN("can't change the device type after a table is bound");
+ goto out;
+ }
+
__unbind(md);
r = __bind(md, table);
@@ -2577,6 +2632,61 @@ int dm_noflush_suspending(struct dm_targ
}
EXPORT_SYMBOL_GPL(dm_noflush_suspending);
+struct dm_md_mempools *dm_alloc_md_mempools(unsigned type)
+{
+ struct dm_md_mempools *pools = kmalloc(sizeof(*pools), GFP_KERNEL);
+
+ if (!pools)
+ return NULL;
+
+ pools->io_pool = (type == DM_TYPE_BIO_BASED) ?
+ mempool_create_slab_pool(MIN_IOS, _io_cache) :
+ mempool_create_slab_pool(MIN_IOS, _rq_bio_info_cache);
+ if (!pools->io_pool)
+ goto free_pools_and_out;
+
+ pools->tio_pool = (type == DM_TYPE_BIO_BASED) ?
+ mempool_create_slab_pool(MIN_IOS, _tio_cache) :
+ mempool_create_slab_pool(MIN_IOS, _rq_tio_cache);
+ if (!pools->tio_pool)
+ goto free_io_pool_and_out;
+
+ pools->bs = (type == DM_TYPE_BIO_BASED) ?
+ bioset_create(16, 0) : bioset_create(MIN_IOS, 0);
+ if (!pools->bs)
+ goto free_tio_pool_and_out;
+
+ return pools;
+
+free_tio_pool_and_out:
+ mempool_destroy(pools->tio_pool);
+
+free_io_pool_and_out:
+ mempool_destroy(pools->io_pool);
+
+free_pools_and_out:
+ kfree(pools);
+
+ return NULL;
+}
+
+void dm_free_md_mempools(struct dm_md_mempools *pools)
+{
+ if (!pools)
+ return;
+
+ if (pools->io_pool)
+ mempool_destroy(pools->io_pool);
+
+ if (pools->tio_pool)
+ mempool_destroy(pools->tio_pool);
+
+ if (pools->bs)
+ bioset_free(pools->bs);
+
+ kfree(pools);
+}
+
static struct block_device_operations dm_blk_dops = {
.open = dm_blk_open,
.release = dm_blk_close,
Index: linux-2.6-block/drivers/md/dm.h
===================================================================
--- linux-2.6-block.orig/drivers/md/dm.h
+++ linux-2.6-block/drivers/md/dm.h
@@ -23,6 +23,13 @@
#define DM_SUSPEND_NOFLUSH_FLAG (1 << 1)
/*
+ * Type of table and mapped_device's mempool
+ */
+#define DM_TYPE_NONE 0
+#define DM_TYPE_BIO_BASED 1
+#define DM_TYPE_REQUEST_BASED 2
+
+/*
* List of devices that a metadevice uses and should open/close.
*/
struct dm_dev_internal {
@@ -32,6 +39,7 @@ struct dm_dev_internal {
};
struct dm_table;
+struct dm_md_mempools;
/*-----------------------------------------------------------------
* Internal table functions.
@@ -48,12 +56,23 @@ void dm_table_postsuspend_targets(struct
int dm_table_resume_targets(struct dm_table *t);
int dm_table_any_congested(struct dm_table *t, int bdi_bits);
int dm_table_any_busy_target(struct dm_table *t);
+int dm_table_set_type(struct dm_table *t);
+unsigned dm_table_get_type(struct dm_table *t);
+bool dm_table_request_based(struct dm_table *t);
+int dm_table_alloc_md_mempools(struct dm_table *t);
+void dm_table_free_md_mempools(struct dm_table *t);
+struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t);
/*
* To check the return value from dm_table_find_target().
*/
#define dm_target_is_valid(t) ((t)->table)
+/*
+ * To check whether the target type is request-based or not (bio-based).
+ */
+#define dm_target_request_based(t) ((t)->type->map_rq != NULL)
+
/*-----------------------------------------------------------------
* A registry of target types.
*---------------------------------------------------------------*/
@@ -98,4 +117,10 @@ void dm_kobject_uevent(struct mapped_dev
int dm_kcopyd_init(void);
void dm_kcopyd_exit(void);
+/*
+ * Mempool operations
+ */
+struct dm_md_mempools *dm_alloc_md_mempools(unsigned type);
+void dm_free_md_mempools(struct dm_md_mempools *pools);
+
#endif
Index: linux-2.6-block/drivers/md/dm-ioctl.c
===================================================================
--- linux-2.6-block.orig/drivers/md/dm-ioctl.c
+++ linux-2.6-block/drivers/md/dm-ioctl.c
@@ -1044,6 +1044,12 @@ static int populate_table(struct dm_tabl
next = spec->next;
}
+ r = dm_table_set_type(table);
+ if (r) {
+ DMWARN("unable to set table type");
+ return r;
+ }
+
return dm_table_complete(table);
}
@@ -1089,6 +1095,13 @@ static int table_load(struct dm_ioctl *p
goto out;
}
+ r = dm_table_alloc_md_mempools(t);
+ if (r) {
+ DMWARN("unable to allocate mempools for this table");
+ dm_table_destroy(t);
+ goto out;
+ }
+
down_write(&_hash_lock);
hc = dm_get_mdptr(md);
if (!hc || hc->md != md) {
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