xfs: merge fsync and O_SYNC handling
The guarantees for O_SYNC are exactly the same as the ones we need to
make for an fsync call (and given that Linux O_SYNC is O_DSYNC the
equivalent is fdadatasync, but we treat both the same in XFS), except
with a range data writeout. Jan Kara has started unifying these two
path for filesystems using the generic helpers, and I've started to
look at XFS.
The actual transaction commited by xfs_fsync and xfs_write_sync_logforce
has a different transaction number, but actually is exactly the same.
We'll only use the fsync transaction going forward. One major difference
is that xfs_write_sync_logforce never issues a cache flush unless we
commit a transaction causing that as a side-effect, which is an obvious
bug in the O_SYNC handling. Second all the locking and i_update_size
vs i_update_core changes from 978b7237123d007b9fa983af6e0e2fa8f97f9934
never made it to xfs_write_sync_logforce, so we add them back.
To make xfs_fsync easily usable from the O_SYNC path, the filemap_fdatawait
call is moved up to xfs_file_fsync, so that we don't wait on the whole
file after we already waited for our portion in xfs_write.
We'll also use a plain call to filemap_write_and_wait_range instead
of the previous sync_page_rang which did it in two steps including
an half-hearted inode write out that doesn't help us.
Once we're done with this also remove the now useless i_update_size
tracking.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index 775249a..ed47fc7 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -68,7 +68,7 @@
#define XFS_TRANS_GROWFS 14
#define XFS_TRANS_STRAT_WRITE 15
#define XFS_TRANS_DIOSTRAT 16
-#define XFS_TRANS_WRITE_SYNC 17
+/* 17 was XFS_TRANS_WRITE_SYNC */
#define XFS_TRANS_WRITEID 18
#define XFS_TRANS_ADDAFORK 19
#define XFS_TRANS_ATTRINVAL 20