Re: [PATCH v2] f2fs: fix sbi->extent_list corruption issue

[Chao Yu]

On 2019/1/9 12:38, Jaegeuk Kim wrote:
> On 01/07, Chao Yu wrote:
>> On 2019/1/5 4:33, Jaegeuk Kim wrote:
>>> On 01/04, Sahitya Tummala wrote:
>>>> On Mon, Nov 26, 2018 at 10:17:20AM +0530, Sahitya Tummala wrote:
>>>>> When there is a failure in f2fs_fill_super() after/during
>>>>> the recovery of fsync'd nodes, it frees the current sbi and
>>>>> retries again. This time the mount is successful, but the files
>>>>> that got recovered before retry, still holds the extent tree,
>>>>> whose extent nodes list is corrupted since sbi and sbi->extent_list
>>>>> is freed up. The list_del corruption issue is observed when the
>>>>> file system is getting unmounted and when those recoverd files extent
>>>>> node is being freed up in the below context.
>>>>>
>>>>> list_del corruption. prev->next should be fffffff1e1ef5480, but was (null)
>>>>> <...>
>>>>> kernel BUG at kernel/msm-4.14/lib/list_debug.c:53!
>>>>> task: fffffff1f46f2280 task.stack: ffffff8008068000
>>>>> lr : __list_del_entry_valid+0x94/0xb4
>>>>> pc : __list_del_entry_valid+0x94/0xb4
>>>>> <...>
>>>>> Call trace:
>>>>> __list_del_entry_valid+0x94/0xb4
>>>>> __release_extent_node+0xb0/0x114
>>>>> __free_extent_tree+0x58/0x7c
>>>>> f2fs_shrink_extent_tree+0xdc/0x3b0
>>>>> f2fs_leave_shrinker+0x28/0x7c
>>>>> f2fs_put_super+0xfc/0x1e0
>>>>> generic_shutdown_super+0x70/0xf4
>>>>> kill_block_super+0x2c/0x5c
>>>>> kill_f2fs_super+0x44/0x50
>>>>> deactivate_locked_super+0x60/0x8c
>>>>> deactivate_super+0x68/0x74
>>>>> cleanup_mnt+0x40/0x78
>>>>> __cleanup_mnt+0x1c/0x28
>>>>> task_work_run+0x48/0xd0
>>>>> do_notify_resume+0x678/0xe98
>>>>> work_pending+0x8/0x14
>>>>>
>>>>> Fix this by cleaning up inodes, extent tree and nodes of those
>>>>> recovered files before freeing up sbi and before next retry.
>>>>>
>>>> Hi Jaegeuk, Chao,
>>>>
>>>> I have observed another scenario where the similar list corruption issue
>>>> can happen with sbi->inode_list as well. If recover_fsync_data()
>>>> fails at some point in write_checkpoint() due to some error and if
>>>> those recovered inodes are still dirty, then after the mount is
>>>> successful, this issue is observed when that dirty inode is under 
>>>> writeback.
>>>
>>> recover_fsync_data() does iget/iput in pair, and destroy_fsync_dnodes() drops
>>> its dirty list and call iput(), when there is an error. So, after then, there'd
>>> be no dirty inodes. If there's no error, checkpoint() flushes quota/dentry pages
>>> in dirty inodes as well. Can we check where this dirty inode came from?
>>
>> I guess it comes from:
>>
>> f2fs_recover_fsync_data()
>>
>> 	/* Needed for iput() to work correctly and not trash data */
>> 	sbi->sb->s_flags |= SB_ACTIVE;
>>
>> iput_final()
>>
>> 	if (!drop && (sb->s_flags & SB_ACTIVE)) {
>> 		inode_add_lru(inode);
>> 		spin_unlock(&inode->i_lock);
>> 		return;
>> 	}
>>
>> So dirty data in those inode can be remained after iput(), then meta/node
>> can be persisted during next checkpoint, if checkpoint failed due to error,
>> dirty inode remain in system. IIUC.
> 
> 
> 749         err = recover_data(sbi, &inode_list, &tmp_inode_list, &dir_list);
> 750         if (!err)
> 751                 f2fs_bug_on(sbi, !list_empty(&inode_list));
> 752         else {
> 753                 /* restore s_flags to let iput() trash data */
> 754                 sbi->sb->s_flags = s_flags;
> 755         }
> 
> We deactivate sb before iput?

We only restore s_flags in error path of recover_data? I remember Sahitya
said his case is encountering error in later checkpoint()?

Thanks,

> 
>>
>>>
>>> Oh, one sceanrio can be an error by f2fs_disable_checkpoint() which will do GC.
>>>
>>>>
>>>> [   90.400500] list_del corruption. prev->next should be ffffffed1f566208, but was (null)
>>>> [   90.675349] Call trace:
>>>> [   90.677869]  __list_del_entry_valid+0x94/0xb4
>>>> [   90.682351]  remove_dirty_inode+0xac/0x114
>>>> [   90.686563]  __f2fs_write_data_pages+0x6a8/0x6c8
>>>> [   90.691302]  f2fs_write_data_pages+0x40/0x4c
>>>> [   90.695695]  do_writepages+0x80/0xf0
>>>> [   90.699372]  __writeback_single_inode+0xdc/0x4ac
>>>> [   90.704113]  writeback_sb_inodes+0x280/0x440
>>>> [   90.708501]  wb_writeback+0x1b8/0x3d0
>>>> [   90.712267]  wb_workfn+0x1a8/0x4d4
>>>> [   90.715765]  process_one_work+0x1c0/0x3d4
>>>> [   90.719883]  worker_thread+0x224/0x344
>>>> [   90.723739]  kthread+0x120/0x130
>>>> [   90.727055]  ret_from_fork+0x10/0x18
>>>>
>>>> I think it is better to cleanup those inodes completely before freeing sbi
>>>> and before next retry as done in this patch. Would you like to re-consider
>>>> this patch for this new issue?
>>>
>>> The patch was merged in mainline already.
>>> Could you take a look at this patch?
>>>
>>> >From cb1d20e640402beed300c2bdce79311ee8a781ad Mon Sep 17 00:00:00 2001
>>> From: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
>>> Date: Fri, 4 Jan 2019 12:29:00 -0800
>>> Subject: [PATCH] f2fs: sync filesystem after roll-forward recovery
>>
>> You mean android kernel mainline?
> 
> I meant the previous patch was upstreamed. We need another patch to address this
> second issue.
> 
> Thanks,
> 
>>
>> Thanks,
>>
>>>
>>> Some works after roll-forward recovery can get an error which will release
>>> all the data structures. Let's flush them in order to make it clean.
>>>
>>> One possible corruption came from:
>>>
>>> [   90.400500] list_del corruption. prev->next should be ffffffed1f566208, but was (null)
>>> [   90.675349] Call trace:
>>> [   90.677869]  __list_del_entry_valid+0x94/0xb4
>>> [   90.682351]  remove_dirty_inode+0xac/0x114
>>> [   90.686563]  __f2fs_write_data_pages+0x6a8/0x6c8
>>> [   90.691302]  f2fs_write_data_pages+0x40/0x4c
>>> [   90.695695]  do_writepages+0x80/0xf0
>>> [   90.699372]  __writeback_single_inode+0xdc/0x4ac
>>> [   90.704113]  writeback_sb_inodes+0x280/0x440
>>> [   90.708501]  wb_writeback+0x1b8/0x3d0
>>> [   90.712267]  wb_workfn+0x1a8/0x4d4
>>> [   90.715765]  process_one_work+0x1c0/0x3d4
>>> [   90.719883]  worker_thread+0x224/0x344
>>> [   90.723739]  kthread+0x120/0x130
>>> [   90.727055]  ret_from_fork+0x10/0x18
>>>
>>> Reported-by: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
>>> Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
>>> ---
>>>  fs/f2fs/super.c | 8 ++++++--
>>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index 547cb7459be7..bb02186293a3 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -3357,7 +3357,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>  	if (test_opt(sbi, DISABLE_CHECKPOINT)) {
>>>  		err = f2fs_disable_checkpoint(sbi);
>>>  		if (err)
>>> -			goto free_meta;
>>> +			goto sync_free_meta;
>>>  	} else if (is_set_ckpt_flags(sbi, CP_DISABLED_FLAG)) {
>>>  		f2fs_enable_checkpoint(sbi);
>>>  	}
>>> @@ -3370,7 +3370,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>  		/* After POR, we can run background GC thread.*/
>>>  		err = f2fs_start_gc_thread(sbi);
>>>  		if (err)
>>> -			goto free_meta;
>>> +			goto sync_free_meta;
>>>  	}
>>>  	kvfree(options);
>>>  
>>> @@ -3392,6 +3392,10 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>  	f2fs_update_time(sbi, REQ_TIME);
>>>  	return 0;
>>>  
>>> +sync_free_meta:
>>> +	/* safe to flush all the data */
>>> +	sync_filesystem(sbi->sb);
>>> +
>>>  free_meta:
>>>  	/* flush dirty orphan inode objects */
>>>  	f2fs_sync_inode_meta(sbi);
>>>
> 
> .
>