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, 6 insertions, 8 deletions

diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 405a65cd9d6b..c962999a87ab 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -983,15 +983,13 @@ xfs_vn_setattr(
                 struct xfs_inode        *ip = XFS_I(d_inode(dentry));
                 uint                    iolock = XFS_IOLOCK_EXCL;
 
-                xfs_ilock(ip, iolock);
-                error = xfs_break_layouts(d_inode(dentry), &iolock, true);
-                if (!error) {
-                        xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
-                        iolock |= XFS_MMAPLOCK_EXCL;
+                error = xfs_break_layouts(d_inode(dentry), &iolock);
+                if (error)
+                        return error;
 
-                        error = xfs_vn_setattr_size(dentry, iattr);
-                }
-                xfs_iunlock(ip, iolock);
+                xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
+                error = xfs_setattr_size(ip, iattr);
+                xfs_iunlock(ip, XFS_MMAPLOCK_EXCL);
         } else {
                 error = xfs_vn_setattr_nonsize(dentry, iattr);
         }