xfs: fix deadlock in xfs_rtfree_extent

To fix the deadlock caused by repeatedly calling xfs_rtfree_extent

 - removed xfs_ilock() and xfs_trans_ijoin() from xfs_rtfree_extent(),
   instead added asserts that the inode is locked and has an inode_item
   attached to it.
 - in xfs_bunmapi() when dealing with an inode with the rt flag
   call xfs_ilock() and xfs_trans_ijoin() so that the
   reference count is bumped on the inode and attached it to the
   transaction before calling into xfs_bmap_del_extent, similar to
   what we do in xfs_bmap_rtalloc.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Reviewed-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_bmap.c

@@ -5124,6 +5124,15 @@ xfs_bunmapi(
 		cur->bc_private.b.flags = 0;
 	} else
 		cur = NULL;
+
+	if (isrt) {
+		/*
+		 * Synchronize by locking the bitmap inode.
+		 */
+		xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL);
+		xfs_trans_ijoin(tp, mp->m_rbmip, XFS_ILOCK_EXCL);
+	}
+
 	extno = 0;
 	while (bno != (xfs_fileoff_t)-1 && bno >= start && lastx >= 0 &&
 	       (nexts == 0 || extno < nexts)) {

fs/xfs/xfs_rtalloc.c

@@ -183,6 +183,7 @@ error_cancel:
 		oblocks = map.br_startoff + map.br_blockcount;
 	}
 	return 0;
+
 error:
 	return error;
 }
@@ -2139,11 +2140,9 @@ xfs_rtfree_extent(
 	xfs_buf_t	*sumbp;		/* summary file block buffer */
 
 	mp = tp->t_mountp;
-	/*
+
-	 * Synchronize by locking the bitmap inode.
+	ASSERT(mp->m_rbmip->i_itemp != NULL);
-	 */
+	ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));
-	xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL);
-	xfs_trans_ijoin(tp, mp->m_rbmip, XFS_ILOCK_EXCL);
 
 #if defined(__KERNEL__) && defined(DEBUG)
 	/*