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, 5 insertions, 9 deletions

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index becf2465dd23..88fd03c66e99 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1251,13 +1251,11 @@ xfs_reflink_remap_range(
                 return -EIO;
 
         /* Lock both files against IO */
-        if (same_inode) {
-                xfs_ilock(src, XFS_IOLOCK_EXCL);
+        lock_two_nondirectories(inode_in, inode_out);
+        if (same_inode)
                 xfs_ilock(src, XFS_MMAPLOCK_EXCL);
-        } else {
-                xfs_lock_two_inodes(src, dest, XFS_IOLOCK_EXCL);
+        else
                 xfs_lock_two_inodes(src, dest, XFS_MMAPLOCK_EXCL);
-        }
 
         /* Don't touch certain kinds of inodes */
         ret = -EPERM;
@@ -1402,11 +1400,9 @@ xfs_reflink_remap_range(
 
 out_unlock:
         xfs_iunlock(src, XFS_MMAPLOCK_EXCL);
-        xfs_iunlock(src, XFS_IOLOCK_EXCL);
-        if (src->i_ino != dest->i_ino) {
+        if (!same_inode)
                 xfs_iunlock(dest, XFS_MMAPLOCK_EXCL);
-                xfs_iunlock(dest, XFS_IOLOCK_EXCL);
-        }
+        unlock_two_nondirectories(inode_in, inode_out);
         if (ret)
                 trace_xfs_reflink_remap_range_error(dest, ret, _RET_IP_);
         return ret;