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authorChris Mason <chris.mason@oracle.com>2009-06-10 15:17:02 -0400
committerChris Mason <chris.mason@oracle.com>2009-06-10 15:17:02 -0400
commite5e9a5206a171b2c467e494aebcdcf70c47289bc (patch)
treed9a6a89cccbd084db923f1661b52d5a1dfdb83fe /fs/btrfs/volumes.h
parent7df336ec1266dccbb253bac52c529d3dcc7c22d0 (diff)
Btrfs: avoid races between super writeout and device list updates
On multi-device filesystems, btrfs writes supers to all of the devices before considering a sync complete. There wasn't any additional locking between super writeout and the device list management code because device management was done inside a transaction and super writeout only happened with no transation writers running. With the btrfs fsync log and other async transaction updates, this has been racey for some time. This adds a mutex to protect the device list. The existing volume mutex could not be reused due to transaction lock ordering requirements. Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/volumes.h')
-rw-r--r--fs/btrfs/volumes.h7
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 3c1f7310421e..5139a833f721 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -96,7 +96,12 @@ struct btrfs_fs_devices {
u64 rw_devices;
u64 total_rw_bytes;
struct block_device *latest_bdev;
- /* all of the devices in the FS */
+
+ /* all of the devices in the FS, protected by a mutex
+ * so we can safely walk it to write out the supers without
+ * worrying about add/remove by the multi-device code
+ */
+ struct mutex device_list_mutex;
struct list_head devices;
/* devices not currently being allocated */