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From: Liu Bo <bo.li.liu@oracle.com>
To: Josef Bacik <jbacik@fusionio.com>
Cc: "linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH 2/5] Btrfs: fix trans block rsv regression
Date: Fri, 14 Sep 2012 21:01:36 +0800	[thread overview]
Message-ID: <50532AB0.2020701@oracle.com> (raw)
In-Reply-To: <20120914124159.GI12994@localhost.localdomain>

On 09/14/2012 08:41 PM, Josef Bacik wrote:
> On Fri, Sep 14, 2012 at 02:58:04AM -0600, Liu Bo wrote:
>> In some workloads we have nested joining transaction operations,
>> eg.
>>   run_delalloc_nocow
>>       btrfs_join_transaction
>>       cow_file_range
>>          btrfs_join_transaction
>>
>> it can be a serious bug since each trans handler has only two
>> block_rsv, orig_rsv and block_rsv, which means we may lose our
>> first block_rsv after two joining transaction operations:
>>
>> 1) btrfs_start_transaction
>>       trans->block_rsv = A
>>
>> 2) btrfs_join_transaction
>>       trans->orig_rsv = trans->block_rsv; ---> orig_rsv is now A
>>       trans->block_rsv = B
>>
>> 3) btrfs_join_transaction
>>       trans->orig_rsv = trans->block_rsv; ---> orig_rsv is now B
>>       trans->block_rsv = C
>>    ...
>>
> 
> I'd like to see the actual stack trace where this happens, because I don't think
> it can happen.  And if it is we need to look at that specific case and adjust it
> as necessary and not add a bunch of kmallocs just to track the block_rsv,
> because frankly it's not that big of a deal, it was just put into place in case
> somebody wasn't expecting a call they made to start another transaction and
> reset the block_rsv, which I don't actually think happens anywhere.  So NAK on
> this patch, give me more information so I can figure out the right way to deal
> with this.  Thanks,
> 

Fine, please run xfstests 068 till it hits a BUG_ON inside either btrfs_delete_delayed_dir_index or
btrfs_insert_delayed_dir_index.

What I saw is that the orig_rsv and block_rsv is both delalloc_block_rsv, which is already lack of space.

thanks,
liubo

> Josef
> --
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> 


  reply	other threads:[~2012-09-14 13:01 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-14  8:58 [PATCH 1/5] Btrfs: fix deadlock with freeze and sync Liu Bo
2012-09-14  8:58 ` [PATCH 2/5] Btrfs: fix trans block rsv regression Liu Bo
2012-09-14 11:15   ` David Sterba
2012-09-14 11:25     ` Liu Bo
2012-09-14 12:07       ` David Sterba
2012-09-14 12:16         ` Liu Bo
2012-09-14 12:41   ` Josef Bacik
2012-09-14 13:01     ` Liu Bo [this message]
2012-09-14 13:05       ` Liu Bo
2012-09-23 10:08         ` Miao Xie
2012-09-14 13:26       ` David Sterba
2012-09-14  8:58 ` [PATCH 3/5] Btrfs: cleanup for duplicated code in find_free_extent Liu Bo
2012-09-14 11:36   ` David Sterba
2012-09-14  8:58 ` [PATCH 4/5] Btrfs: cleanup fs_info->hashers Liu Bo
2012-09-14 11:21   ` David Sterba
2012-09-14  8:58 ` [PATCH 5/5] Btrfs: kill obsolete arguments in btrfs_wait_ordered_extents Liu Bo
2012-09-14 12:45   ` Josef Bacik
2012-09-14 12:55     ` Liu Bo
2012-09-14 13:01       ` Josef Bacik
2012-09-14 13:09     ` David Sterba
2012-09-14 10:07 ` [PATCH 1/5] Btrfs: fix deadlock with freeze and sync Miao Xie
2012-09-14 11:30   ` Liu Bo
2012-09-14 12:42 ` Josef Bacik
2012-09-14 13:03   ` Liu Bo
2012-09-14 14:41 ` Josef Bacik

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