[libvirt] [PATCH v2] storage: Allow --shrink for raw type volume of fs pool

[Osier Yang]

There is no need to use posix_fallocate or SYS_fallocate to shrink
the volume, ftruncate can do the work. qemu-img/kvm-img supports to
shrink the volume itself.

And instead of bool arguments, this introduces virStorageFileResizeFlags
enum.
---
 src/storage/storage_backend_fs.c | 18 ++++++++++++++----
 src/util/virstoragefile.c        |  5 +++--
 src/util/virstoragefile.h        |  7 ++++++-
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/src/storage/storage_backend_fs.c b/src/storage/storage_backend_fs.c
index b1efa50..e55148c 100644
--- a/src/storage/storage_backend_fs.c
+++ b/src/storage/storage_backend_fs.c
@@ -1246,15 +1246,25 @@ virStorageBackendFileSystemVolResize(virConnectPtr conn ATTRIBUTE_UNUSED,
                                      unsigned long long capacity,
                                      unsigned int flags)
 {
-    virCheckFlags(VIR_STORAGE_VOL_RESIZE_ALLOCATE, -1);
+    unsigned int resize_flags = 0;
+    bool preallocate = false;
 
-    bool pre_allocate = flags & VIR_STORAGE_VOL_RESIZE_ALLOCATE;
+    virCheckFlags(VIR_STORAGE_VOL_RESIZE_ALLOCATE |
+                  VIR_STORAGE_VOL_RESIZE_SHRINK, -1);
+
+    if (flags & VIR_STORAGE_VOL_RESIZE_ALLOCATE) {
+        resize_flags |= VIR_STORAGE_FILE_RESIZE_PREALLOCATE;
+        preallocate = true;
+    }
+
+    if (flags & VIR_STORAGE_VOL_RESIZE_SHRINK)
+        resize_flags |= VIR_STORAGE_FILE_RESIZE_SHRINK;
 
     if (vol->target.format == VIR_STORAGE_FILE_RAW) {
         return virStorageFileResize(vol->target.path, capacity,
-                                    vol->capacity, pre_allocate);
+                                    vol->capacity, resize_flags);
     } else {
-        if (pre_allocate) {
+        if (preallocate) {
             virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
                            _("preallocate is only supported for raw "
                              "type volume"));
diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index bf668c8..9e085d4 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -1044,7 +1044,7 @@ int
 virStorageFileResize(const char *path,
                      unsigned long long capacity,
                      unsigned long long orig_capacity,
-                     bool pre_allocate)
+                     unsigned int flags)
 {
     int fd = -1;
     int ret = -1;
@@ -1057,7 +1057,8 @@ virStorageFileResize(const char *path,
         goto cleanup;
     }
 
-    if (pre_allocate) {
+    if (flags & VIR_STORAGE_FILE_RESIZE_PREALLOCATE &&
+        !(flags & VIR_STORAGE_FILE_RESIZE_SHRINK)) {
 #if HAVE_POSIX_FALLOCATE
         if ((rc = posix_fallocate(fd, offset, len)) != 0) {
             virReportSystemError(rc,
diff --git a/src/util/virstoragefile.h b/src/util/virstoragefile.h
index c195c9a..1cf90ce 100644
--- a/src/util/virstoragefile.h
+++ b/src/util/virstoragefile.h
@@ -89,10 +89,15 @@ const char *virStorageFileChainLookup(virStorageFileMetadataPtr chain,
 
 void virStorageFileFreeMetadata(virStorageFileMetadataPtr meta);
 
+enum {
+    VIR_STORAGE_FILE_RESIZE_PREALLOCATE = 1 << 0,
+    VIR_STORAGE_FILE_RESIZE_SHRINK      = 1 << 1,
+} virStorageFileResizeFlags;
+
 int virStorageFileResize(const char *path,
                          unsigned long long capacity,
                          unsigned long long orig_capacity,
-                         bool pre_allocate);
+                         unsigned int flags);
 
 enum {
     VIR_STORAGE_FILE_SHFS_NFS = (1 << 0),
-- 
1.8.1.4