Re: [PATCH 3/6] btrfs-progs: Don't report dirty leaked eb using BUG_ON

[Qu Wenruo <quwenruo.btrfs@gmx.com>]

On 2018/8/29 下午10:52, Nikolay Borisov wrote:
> 
> 
> On  3.08.2018 08:50, Qu Wenruo wrote:
>> Another BUG_ON() during fuzz/003:
>> ------
>> ====== RUN MAYFAIL /home/adam/btrfs/btrfs-progs/btrfs check --init-csum-tree /home/adam/btrfs/btrfs-progs/tests//fuzz-tests/images/bko-161821.raw.restored
>> [1/7] checking root items
>> Fixed 0 roots.
>> [2/7] checking extents
>> parent transid verify failed on 4198400 wanted 14 found 1114126
>> parent transid verify failed on 4198400 wanted 14 found 1114126
>> Ignoring transid failure
>> owner ref check failed [4198400 4096]
>> repair deleting extent record: key [4198400,169,0]
>> adding new tree backref on start 4198400 len 4096 parent 0 root 5
>> Repaired extent references for 4198400
>> ref mismatch on [4222976 4096] extent item 1, found 0
>> backref 4222976 root 7 not referenced back 0x5617f8ecf780
>> incorrect global backref count on 4222976 found 1 wanted 0
>> backpointer mismatch on [4222976 4096]
>> owner ref check failed [4222976 4096]
>> repair deleting extent record: key [4222976,169,0]
>> Repaired extent references for 4222976
>> [3/7] checking free space cache
>> [4/7] checking fs roots
>> parent transid verify failed on 4198400 wanted 14 found 1114126
>> Ignoring transid failure
>> Wrong generation of child node/leaf, wanted: 1114126, have: 14
>> root 5 missing its root dir, recreating
>> parent transid verify failed on 4198400 wanted 14 found 1114126
>> Ignoring transid failure
>> ERROR: child eb corrupted: parent bytenr=4222976 item=0 parent level=1 child level=2
>> ERROR: errors found in fs roots
>> extent buffer leak: start 4222976 len 4096
>> extent_io.c:611: free_extent_buffer_internal: BUG_ON `eb->flags & EXTENT_DIRTY` triggered, value 1
>> failed (ignored, ret=134): /home/adam/btrfs/btrfs-progs/btrfs check --init-csum-tree /home/adam/btrfs/btrfs-progs/tests//fuzz-tests/images/bko-161821.raw.restored
>> mayfail: returned code 134 (SIGABRT), not ignored
>> test failed for case 003-multi-check-unmounted
>> ------
>>
>> Since we're shifting to using btrfs_abort_transaction() in btrfs-progs,
>> it will be more and more common to see dirty leaked eb.
>> Instead of BUG_ON(), we only needs to report it as warning.
> 
> 
> So how are such leaked extents supposed to be cleaned? So when
> transaction_aborted is set we just return some errors from various
> functions but I don't see how modified extents in the transaction are freed?

They're freed by extent_io_tree_cleanup(), called by the following call
trace:
close_ctree_fs_info()
|- btrfs_cleanup_all_caches()
   |- extent_io_tree_cleanup(&fs_info->extent_cache)
      |- free_extent_buffer_nocache()

And inside extent_io_tree_cleanup(), it's also where we do leaked extent
buffer detection.

Thanks,
Qu

>>
>> Signed-off-by: Qu Wenruo <wqu@suse.com>
>> ---
>>  extent_io.c | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/extent_io.c b/extent_io.c
>> index 198492699438..b8510b0ae94e 100644
>> --- a/extent_io.c
>> +++ b/extent_io.c
>> @@ -608,7 +608,11 @@ static void free_extent_buffer_internal(struct extent_buffer *eb, bool free_now)
>>  	eb->refs--;
>>  	BUG_ON(eb->refs < 0);
>>  	if (eb->refs == 0) {
>> -		BUG_ON(eb->flags & EXTENT_DIRTY);
>> +		if (eb->flags & EXTENT_DIRTY) {
>> +			warning(
>> +			"dirty eb leak (aborted trans): start %llu len %u",
>> +				eb->start, eb->len);
>> +		}
>>  		list_del_init(&eb->recow);
>>  		if (eb->flags & EXTENT_BUFFER_DUMMY || free_now)
>>  			free_extent_buffer_final(eb);
>>