From: Su Yue <suy.f...@cn.fujitsu.com>

After call of check_inode_item(), path may point to the last unchecked
slot of the leaf. The outer walk_up_tree() always treats the position
as checked item then skips to next item.

If the last item was an inode item, yes, it was unchecked.
Then walk_up_tree() will think the leaf is checked and walk up to
upper node, process_one_leaf() in walk_down_tree() would skip to
check next inode item. Which means, the inode item won't be checked.

Solution:
After check_inode_item returns, if found path point to the last item
of a leaf, decrease path slot manually, so walk_up_tree() will stay
on the leaf.

Fixes: 5e2dc770471b ("btrfs-progs: check: skip shared node or leaf check for 
low_memory mode")
Signed-off-by: Su Yue <suy.f...@cn.fujitsu.com>
---
 check/mode-lowmem.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c
index 8fc9edab1d66..b6b33786d02b 100644
--- a/check/mode-lowmem.c
+++ b/check/mode-lowmem.c
@@ -2612,6 +2612,18 @@ again:
        if (cur->start == cur_bytenr)
                goto again;
 
+       /*
+        * path may point at the last item(a inode item maybe) in a leaf.
+        * Without below lines, walk_up_tree() will skip the item which
+        * means all items related to the inode will never be checked.
+        * Decrease the slot manually, walk_up_tree won't skip to next node
+        * if it occurs.
+        */
+       if (path->slots[0] + 1 >= btrfs_header_nritems(path->nodes[0])) {
+               if (path->slots[0])
+                       path->slots[0]--;
+       }
+
        /*
         * we have switched to another leaf, above nodes may
         * have changed, here walk down the path, if a node
-- 
2.18.0

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