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* [PATCH] btrfs: pass a valid btrfs_tree_parent_check when possible
@ 2026-04-09 23:16 Qu Wenruo
  2026-04-10  0:03 ` Boris Burkov
  0 siblings, 1 reply; 2+ messages in thread
From: Qu Wenruo @ 2026-04-09 23:16 UTC (permalink / raw)
  To: linux-btrfs

Commit 6e181cfe2409 ("btrfs: revalidate cached tree blocks on the
uptodate path") introduced the @check parameter for
btrfs_buffer_uptodate() to allow re-validation of a cached extent
buffer.

But there are still call sites that doesn't utilize this parameter,
which exposes them to possible corrupted tree blocks, e.g. an empty
child leaf of a parent node, which should be rejected by
btrfs_verify_level_key() but if @check is NULL such check will be
skipped and cause problems.

Thankfully for a lot of cases there is already an existing @check
structure around and we can pass it directly to btrfs_buffer_uptodate().

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/ctree.c       | 16 +++++-----------
 fs/btrfs/extent-tree.c | 11 ++++++++---
 fs/btrfs/extent_io.c   |  2 +-
 3 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index d70da290bedf..829d8be7f423 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1497,17 +1497,11 @@ read_block_for_search(struct btrfs_root *root, struct btrfs_path *p,
 		if (p->reada == READA_FORWARD_ALWAYS)
 			reada_for_search(fs_info, p, parent_level, slot, key->objectid);
 
-		/* first we do an atomic uptodate check */
-		if (btrfs_buffer_uptodate(tmp, check.transid, NULL) > 0) {
-			/*
-			 * Do extra check for first_key, eb can be stale due to
-			 * being cached, read from scrub, or have multiple
-			 * parents (shared tree blocks).
-			 */
-			if (unlikely(btrfs_verify_level_key(tmp, &check))) {
-				ret = -EUCLEAN;
-				goto out;
-			}
+		/* Check if the cached eb is uptodate. */
+		ret = btrfs_buffer_uptodate(tmp, check.transid, &check);
+		if (unlikely(ret < 0))
+			goto out;
+		if (ret > 0) {
 			*eb_ret = tmp;
 			tmp = NULL;
 			ret = 0;
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 391fad41c3b6..5d5b42ea4ade 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5781,16 +5781,21 @@ static int check_next_block_uptodate(struct btrfs_trans_handle *trans,
 
 	generation = btrfs_node_ptr_generation(path->nodes[level], path->slots[level]);
 
-	if (btrfs_buffer_uptodate(next, generation, NULL))
-		return 0;
-
 	check.level = level - 1;
 	check.transid = generation;
 	check.owner_root = btrfs_root_id(root);
 	check.has_first_key = true;
 	btrfs_node_key_to_cpu(path->nodes[level], &check.first_key, path->slots[level]);
 
+	ret = btrfs_buffer_uptodate(next, generation, &check);
+	if (ret > 0)
+		return 0;
 	btrfs_tree_unlock(next);
+	if (ret < 0) {
+		free_extent_buffer(next);
+		return ret;
+	}
+
 	if (level == 1)
 		reada_walk_down(trans, root, wc, path);
 	ret = btrfs_read_extent_buffer(next, &check);
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a8887285deda..3f59fb0a9ee5 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4648,7 +4648,7 @@ void btrfs_readahead_tree_block(struct btrfs_fs_info *fs_info,
 	if (IS_ERR(eb))
 		return;
 
-	if (btrfs_buffer_uptodate(eb, gen, NULL)) {
+	if (btrfs_buffer_uptodate(eb, gen, &check)) {
 		free_extent_buffer(eb);
 		return;
 	}
-- 
2.53.0


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2026-04-09 23:16 [PATCH] btrfs: pass a valid btrfs_tree_parent_check when possible Qu Wenruo
2026-04-10  0:03 ` Boris Burkov

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