From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([59.151.112.132]:56569 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751687AbbHYCrD (ORCPT ); Mon, 24 Aug 2015 22:47:03 -0400 From: Qu Wenruo To: CC: Subject: [PATCH 2/2] btrfs-progs: find-root: Fix a bug that will cause wrong result Date: Tue, 25 Aug 2015 10:44:57 +0800 Message-ID: <1440470697-21177-2-git-send-email-quwenruo@cn.fujitsu.com> In-Reply-To: <1440470697-21177-1-git-send-email-quwenruo@cn.fujitsu.com> References: <1440470697-21177-1-git-send-email-quwenruo@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-btrfs-owner@vger.kernel.org List-ID: [BUG] btrfs-find-root may not output desire result, as due to search_extent_cache() may return result which 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 judgment to make sure the search_extent_cache() is returning desired result. Reported-by: Marc Merlin Signed-off-by: Qu Wenruo --- find-root.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/find-root.c b/find-root.c index 1af37b5..0eca0ab 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 doesn't cover + * the range. So need extra judgement to make sure it's a match. + */ 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; -- 2.5.0