[PATCH 4/4] V2 xfs: fix deadlock in xfs_rtfree_extent with kernel v2.6.37

[Kamal Dasu <kdasu.kdev@gmail.com>]

To fix the deadlock caused by recursively calling xfs_rtfree_extent
from xfs_bunmapi():

 - removed  xfs_trans_iget() 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>
---
 fs/xfs/xfs_bmap.c    |   10 ++++++++++
 fs/xfs/xfs_rtalloc.c |   13 ++++++-------
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index 36c317c..103a253 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -5058,6 +5058,16 @@ 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_ref(tp, mp->m_rbmip,
+                                   XFS_ILOCK_EXCL | XFS_ILOCK_RTBITMAP);
+       }
+
        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 f592ac9..d0a48d4 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -2160,13 +2160,12 @@ xfs_rtfree_extent(
        xfs_buf_t       *sumbp;         /* summary file block buffer */
 
        mp = tp->t_mountp;
-       /*
-        * Synchronize by locking the bitmap inode.
-        */
-       error = xfs_trans_iget(mp, tp, mp->m_sb.sb_rbmino, 0,
-                              XFS_ILOCK_EXCL | XFS_ILOCK_RTBITMAP, &ip);
-       if (error)
-               return error;
+
+       ASSERT(mp->m_rbmip->i_itemp != NULL);
+       ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));
+
+       ip = mp->m_rbmip;
+
 #if defined(__KERNEL__) && defined(DEBUG)
        /*
         * Check to see that this whole range is currently allocated.
-- 
1.7.5.4

-- 
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