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author | Sage Weil <sage@newdream.net> | 2008-06-10 14:07:39 (GMT) |
---|---|---|
committer | Chris Mason <chris.mason@oracle.com> | 2008-09-25 15:04:03 (GMT) |
commit | 6bf13c0cc833bf5ba013d6aa60379484bf48c4e6 (patch) | |
tree | ae2b54a1a26a89fece49f6b6d6dff8448efab542 /fs/btrfs/super.c | |
parent | eba12c7bfcb4855fc757357e5e5b0b9a474499ba (diff) | |
download | linux-fsl-qoriq-6bf13c0cc833bf5ba013d6aa60379484bf48c4e6.tar.xz |
Btrfs: transaction ioctls
These ioctls let a user application hold a transaction open while it
performs a series of operations. A final ioctl does a sync on the fs
(closing the current transaction). This is the main requirement for
Ceph's OSD to be able to keep the data it's storing in a btrfs volume
consistent, and AFAICS it works just fine. The application would do
something like
fd = ::open("some/file", O_RDONLY);
::ioctl(fd, BTRFS_IOC_TRANS_START);
/* do a bunch of stuff */
::ioctl(fd, BTRFS_IOC_TRANS_END);
or just
::close(fd);
And to ensure it commits to disk,
::ioctl(fd, BTRFS_IOC_SYNC);
When a transaction is held open, the trans_handle is attached to the
struct file (via private_data) so that it will get cleaned up if the
process dies unexpectedly. A held transaction is also ended on fsync() to
avoid a deadlock.
A misbehaving application could also deliberately hold a transaction open,
effectively locking up the FS, so it may make sense to restrict something
like this to root or something.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/super.c')
-rw-r--r-- | fs/btrfs/super.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 77f4449..39bb869 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -293,7 +293,7 @@ fail_close: return err; } -static int btrfs_sync_fs(struct super_block *sb, int wait) +int btrfs_sync_fs(struct super_block *sb, int wait) { struct btrfs_trans_handle *trans; struct btrfs_root *root; |