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, 4 deletions

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 9c3e5c6ddf20..ff4d6311c7f4 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -70,8 +70,6 @@ xfs_inode_alloc(
         ASSERT(!xfs_isiflocked(ip));
         ASSERT(ip->i_ino == 0);
 
-        mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
-
         /* initialise the xfs inode */
         ip->i_ino = ino;
         ip->i_mount = mp;
@@ -394,8 +392,8 @@ xfs_iget_cache_hit(
                 xfs_inode_clear_reclaim_tag(pag, ip->i_ino);
                 inode->i_state = I_NEW;
 
-                ASSERT(!rwsem_is_locked(&ip->i_iolock.mr_lock));
-                mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
+                ASSERT(!rwsem_is_locked(&inode->i_rwsem));
+                init_rwsem(&inode->i_rwsem);
 
                 spin_unlock(&ip->i_flags_lock);
                 spin_unlock(&pag->pag_ici_lock);