[PATCH] xfs: fix deadlock in xfs_rtfree_extent with kernel v3.x

["Kamal Dasu" <kdasu.kdev@xxxxxxxxx>]

To fix the deadlock caused by recursively 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@xxxxxxxxx>
---
 fs/xfs/xfs_bmap.c    |    9 +++++++++
 fs/xfs/xfs_rtalloc.c |    9 ++++-----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index 188ef2f..9a0aa33 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/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)) {
diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index 87323f1..ca4f315 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/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.
-        */
-       xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL);
-       xfs_trans_ijoin(tp, mp->m_rbmip, XFS_ILOCK_EXCL);
+
+       ASSERT(mp->m_rbmip->i_itemp != NULL);
+       ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));
 
 #if defined(__KERNEL__) && defined(DEBUG)
        /*
-- 
1.7.5.4