linux-kernel - [PATCH AUTOSEL 5.4] btrfs: convert BUG_ON in btrfs_reloc_cow

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Message-Id: <20250126144933.925681-1-sashal@kernel.org>
Date: Sun, 26 Jan 2025 09:49:33 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Josef Bacik <josef@...icpanda.com>,
	Boris Burkov <boris@....io>,
	David Sterba <dsterba@...e.com>,
	Sasha Levin <sashal@...nel.org>,
	clm@...com,
	linux-btrfs@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4] btrfs: convert BUG_ON in btrfs_reloc_cow_block() to proper error handling

From: Josef Bacik <josef@...icpanda.com>

[ Upstream commit 6a4730b325aaa48f7a5d5ba97aff0a955e2d9cec ]

This BUG_ON is meant to catch backref cache problems, but these can
arise from either bugs in the backref cache or corruption in the extent
tree.  Fix it to be a proper error.

Reviewed-by: Boris Burkov <boris@....io>
Signed-off-by: Josef Bacik <josef@...icpanda.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/btrfs/relocation.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 89ad7e12c08bb..062154c6a65f6 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -4789,8 +4789,18 @@ int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
 		WARN_ON(!first_cow && level == 0);
 
 		node = rc->backref_cache.path[level];
-		BUG_ON(node->bytenr != buf->start &&
-		       node->new_bytenr != buf->start);
+
+		/*
+		 * If node->bytenr != buf->start and node->new_bytenr !=
+		 * buf->start then we've got the wrong backref node for what we
+		 * expected to see here and the cache is incorrect.
+		 */
+		if (unlikely(node->bytenr != buf->start && node->new_bytenr != buf->start)) {
+			btrfs_err(fs_info,
+"bytenr %llu was found but our backref cache was expecting %llu or %llu",
+				  buf->start, node->bytenr, node->new_bytenr);
+			return -EUCLEAN;
+		}
 
 		drop_node_buffer(node);
 		extent_buffer_get(cow);
-- 
2.39.5