From 27260dd1904bb409cf84709928ba9bc5506fbe8e Mon Sep 17 00:00:00 2001 From: Sun YangKai Date: Thu, 12 Jun 2025 16:32:23 +0800 Subject: [PATCH] btrfs: remove partial support for lowest level from btrfs_search_forward() Commit 323ac95bce44 ("Btrfs: don't read leaf blocks containing only checksums during truncate") changed the condition from `level == 0` to `level == path->lowest_level`, while its original purpose was just to do some leaf node handling (calling btrfs_item_key_to_cpu()) and skip some code that doesn't fit leaf nodes. After changing the condition, the code path: 1. Also handles the non-leaf nodes when path->lowest_level is nonzero, which is wrong. However btrfs_search_forward() is never called with a nonzero path->lowest_level, which makes this bug not found before. 2. Makes the later if block with the same condition, which was originally used to handle non-leaf node (calling btrfs_node_key_to_cpu()) when lowest_level is not zero, dead code. Since btrfs_search_forward() is never called for a path with a lowest_level different from zero, just completely remove the partial support for a non-zero lowest_level, simplifying a bit the code, and assert that lowest_level is zero at the start of the function. Suggested-by: Qu Wenruo Fixes: 323ac95bce44 ("Btrfs: don't read leaf blocks containing only checksums during truncate") Reviewed-by: Filipe Manana Signed-off-by: Sun YangKai Signed-off-by: David Sterba --- fs/btrfs/ctree.c | 18 +++++------------- 1 file changed, 5 insertions(+), 13 deletions(-) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 1b36ee2d80448..2997f24207195 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -4594,16 +4594,13 @@ int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root, /* * A helper function to walk down the tree starting at min_key, and looking - * for nodes or leaves that are have a minimum transaction id. + * for leaves that have a minimum transaction id. * This is used by the btree defrag code, and tree logging * * This does not cow, but it does stuff the starting key it finds back * into min_key, so you can call btrfs_search_slot with cow=1 on the * key and get a writable path. * - * This honors path->lowest_level to prevent descent past a given level - * of the tree. - * * min_trans indicates the oldest transaction that you are interested * in walking through. Any nodes or leaves older than min_trans are * skipped over (without reading them). @@ -4624,6 +4621,7 @@ int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key, int keep_locks = path->keep_locks; ASSERT(!path->nowait); + ASSERT(path->lowest_level == 0); path->keep_locks = 1; again: cur = btrfs_read_lock_root_node(root); @@ -4645,8 +4643,8 @@ again: goto out; } - /* at the lowest level, we're done, setup the path and exit */ - if (level == path->lowest_level) { + /* At level 0 we're done, setup the path and exit. */ + if (level == 0) { if (slot >= nritems) goto find_next_key; ret = 0; @@ -4687,12 +4685,6 @@ find_next_key: goto out; } } - if (level == path->lowest_level) { - ret = 0; - /* Save our key for returning back. */ - btrfs_node_key_to_cpu(cur, min_key, slot); - goto out; - } cur = btrfs_read_node_slot(cur, slot); if (IS_ERR(cur)) { ret = PTR_ERR(cur); @@ -4708,7 +4700,7 @@ find_next_key: out: path->keep_locks = keep_locks; if (ret == 0) - btrfs_unlock_up_safe(path, path->lowest_level + 1); + btrfs_unlock_up_safe(path, 1); return ret; } -- 2.47.2