xfs: remove i_iolock and use i_rwsem in the VFS inode instead

This patch drops the XFS-own i_iolock and uses the VFS i_rwsem which
recently replaced i_mutex instead.  This means we only have to take
one lock instead of two in many fast path operations, and we can
also shrink the xfs_inode structure.  Thanks to the xfs_ilock family
there is very little churn, the only thing of note is that we need
to switch to use the lock_two_directory helper for taking the i_rwsem
on two inodes in a few places to make sure our lock order matches
the one used in the VFS.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 2 insertions, 5 deletions

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index ab266d66124d..e8f6c2bcd4a4 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1585,7 +1585,6 @@ xfs_vm_bmap(
         struct xfs_inode        *ip = XFS_I(inode);
 
         trace_xfs_vm_bmap(XFS_I(inode));
-        xfs_ilock(ip, XFS_IOLOCK_SHARED);
 
         /*
          * The swap code (ab-)uses ->bmap to get a block mapping and then
@@ -1593,12 +1592,10 @@ xfs_vm_bmap(
          * that on reflinks inodes, so we have to skip out here.  And yes,
          * 0 is the magic code for a bmap error..
          */
-        if (xfs_is_reflink_inode(ip)) {
-                xfs_iunlock(ip, XFS_IOLOCK_SHARED);
+        if (xfs_is_reflink_inode(ip))
                 return 0;
-        }
+
         filemap_write_and_wait(mapping);
-        xfs_iunlock(ip, XFS_IOLOCK_SHARED);
         return generic_block_bmap(mapping, block, xfs_get_blocks);
 }