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btrfs-progs: find-root: fix a bug that will cause wrong result

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[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 <marc@merlins.org>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2015-08-25 10:44:57 +08:00 committed by David Sterba
parent 3eb8836424
commit 004eabb1ad
1 changed files with 7 additions and 2 deletions
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9
find-root.c
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@ -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;