From 004eabb1ad09171389b7e9260342758e7b331a07 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Tue, 25 Aug 2015 10:44:57 +0800 Subject: btrfs-progs: find-root: fix a bug that will cause wrong result [BUG] btrfs-find-root may not output desire result, as due to search_extent_cache() may return a result that doesn't cover the desired range, generation cache can be screwed up if higher generation tree root is found before lower generation tree root. For example: ======= ./btrfs-find-root /dev/sda6 -a Superblock thinks the generation is 8 Superblock thinks the level is 0 adding bytenr: 4194304, gen: 8 <<< Debug output adding bytenr: 24715264, gen: 7 <<< gen is 7 at read_tree_block time Well block 4194304(gen: 8 level: 0) seems good, and it matches superblock Well block 24715264(gen: 8 level: 0) seems good, and it matches superblock <<< But its gen is wrong at result output time ======= [Fix] Add a new check to make sure the search_extent_cache() is returning the desired result. Reported-by: Marc Merlin Signed-off-by: Qu Wenruo Signed-off-by: David Sterba --- find-root.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'find-root.c') diff --git a/find-root.c b/find-root.c index 1af37b54..55e79423 100644 --- a/find-root.c +++ b/find-root.c @@ -46,9 +46,14 @@ static int add_eb_to_result(struct extent_buffer *eb, generation < filter->generation) return ret; - /* Get the generation cache or create one */ + /* + * Get the generation cache or create one + * + * NOTE: search_cache_extent() may return cache that doesn't cover + * the range. So we need an extra check to make sure it's the right one. + */ cache = search_cache_extent(result, generation); - if (!cache) { + if (!cache || cache->start != generation) { gen_cache = malloc(sizeof(*gen_cache)); BUG_ON(!gen_cache); cache = &gen_cache->cache; -- cgit v1.2.3