[PATCH] xfs: v2 fix node forward in xfs_node_toosmall

[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.

Signed-off-by: Mark Tinguely <tinguely@xxxxxxx>
---
 v2 -> Dave's local variable approach.
    -> send to -stable this bug is in 3.10 and 3.11

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

Index: b/fs/xfs/xfs_da_btree.c
===================================================================
--- 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;
                else
@@ -1236,10 +1237,10 @@ xfs_da3_node_toosmall(
                        return(error);
 
                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) {