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[PATCH] xfs: fix node forward in xfs_node_toosmall

To: stable@xxxxxxxxxxxxxxx
Subject: [PATCH] xfs: fix node forward in xfs_node_toosmall
From: Ben Myers <bpm@xxxxxxx>
Date: Tue, 8 Oct 2013 19:09:26 -0500
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
User-agent: Mutt/1.5.20 (2009-06-14)
From: Mark Tinguely <tinguely@xxxxxxx>

Commit f5ea1100 cleans up the disk to host conversions for
node directory entries, but because a variable is reused in
xfs_node_toosmall() the next node is not correctly found.
If the original node is small enough (<= 3/8 of the node size),
this change may incorrectly cause a node collapse when it should
not. That will cause an assert in xfstest generic/319:

   Assertion failed: first <= last && last < BBTOB(bp->b_length),
   file: /root/newest/xfs/fs/xfs/xfs_trans_buf.c, line: 569

Keep the original node header to get the correct forward node.

(When a node is considered for a merge with a sibling, it overwrites the
 sibling pointers of the original incore nodehdr with the sibling's
 pointers.  This leads to loop considering the original node as a merge
 candidate with itself in the second pass, and so it incorrectly
 determines a merge should occur.)

upstream commit 997def25e4b9cee3b01609e18a52f926bca8bd2b

Signed-off-by: Mark Tinguely <tinguely@xxxxxxx>
Reviewed-by: Ben Myers <bpm@xxxxxxx>
Signed-off-by: Ben Myers <bpm@xxxxxxx>

[v3: added Dave Chinner's (slightly modified) suggestion to the commit header,
        cleaned up whitespace.  -bpm]

Hi Stable Folk,

   Please take this commit for stable branches back to 3.10.  This fixes a bug
   in XFS directory code.


 fs/xfs/xfs_da_btree.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_da_btree.c b/fs/xfs/xfs_da_btree.c
index 069537c..20bf8e8 100644
--- a/fs/xfs/xfs_da_btree.c
+++ b/fs/xfs/xfs_da_btree.c
@@ -1224,6 +1224,7 @@ xfs_da3_node_toosmall(
        /* start with smaller blk num */
        forward = nodehdr.forw < nodehdr.back;
        for (i = 0; i < 2; forward = !forward, i++) {
+               struct xfs_da3_icnode_hdr thdr;
                if (forward)
                        blkno = nodehdr.forw;
@@ -1236,10 +1237,10 @@ xfs_da3_node_toosmall(
                node = bp->b_addr;
-               xfs_da3_node_hdr_from_disk(&nodehdr, node);
+               xfs_da3_node_hdr_from_disk(&thdr, node);
                xfs_trans_brelse(state->args->trans, bp);
-               if (count - nodehdr.count >= 0)
+               if (count - thdr.count >= 0)
                        break;  /* fits with at least 25% to spare */
        if (i >= 2) {

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