[PATCH 5/6] btrfs-progs: lowmem: continue to check item in last slot while checking inodes

[damenly.su@gmail.com]

From: Su Yue <suy.fnst@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.fnst@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