xfs: don't block inode reclaim on the ILOCK

When we attempt to reclaim an inode, the first thing we do is take
the inode lock. This is blocking right now, so if the inode being
accessed by something else (e.g. being flushed to the cluster
buffer) we will block here.

Change this to a trylock so that we do not block inode reclaim
unnecessarily here.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_icache.c

@@ -1119,9 +1119,10 @@ xfs_reclaim_inode(
 {
 	xfs_ino_t		ino = ip->i_ino; /* for radix_tree_delete */
 
-	xfs_ilock(ip, XFS_ILOCK_EXCL);
-	if (!xfs_iflock_nowait(ip))
+	if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
 		goto out;
+	if (!xfs_iflock_nowait(ip))
+		goto out_iunlock;
 
 	if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {
 		xfs_iunpin_wait(ip);
@@ -1188,8 +1189,9 @@ xfs_reclaim_inode(
 
 out_ifunlock:
 	xfs_ifunlock(ip);
-out:
+out_iunlock:
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+out:
 	xfs_iflags_clear(ip, XFS_IRECLAIM);
 	return false;
 }