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>

1 files changed, 3 insertions, 8 deletions

diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
index ceecafd1f9c1..03d3100559ac 100644
--- a/fs/xfs/xfs_vnodeops.c
+++ b/fs/xfs/xfs_vnodeops.c
@@ -611,7 +611,7 @@ xfs_fsync(
         xfs_inode_t     *ip)
 {
         xfs_trans_t     *tp;
-        int             error;
+        int             error = 0;
         int             log_flushed = 0, changed = 1;
 
         xfs_itrace_entry(ip);
@@ -619,14 +619,9 @@ xfs_fsync(
         if (XFS_FORCED_SHUTDOWN(ip->i_mount))
                 return XFS_ERROR(EIO);
 
-        /* capture size updates in I/O completion before writing the inode. */
-        error = xfs_wait_on_pages(ip, 0, -1);
-        if (error)
-                return XFS_ERROR(error);
-
         /*
          * We always need to make sure that the required inode state is safe on
-         * disk.  The vnode might be clean but we still might need to force the
+         * disk.  The inode might be clean but we still might need to force the
          * log because of committed transactions that haven't hit the disk yet.
          * Likewise, there could be unflushed non-transactional changes to the
          * inode core that have to go to disk and this requires us to issue
@@ -638,7 +633,7 @@ xfs_fsync(
          */
         xfs_ilock(ip, XFS_ILOCK_SHARED);
 
-        if (!(ip->i_update_size || ip->i_update_core)) {
+        if (!ip->i_update_core) {
                 /*
                  * Timestamps/size haven't changed since last inode flush or
                  * inode transaction commit.  That means either nothing got