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Subject: Re: [PATCH v2] f2fs: fix sbi->extent_list corruption issue
To:     Jaegeuk Kim <jaegeuk@kernel.org>
CC:     Sahitya Tummala <stummala@codeaurora.org>,
        <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>
References: <20181127003050.GG55960@jaegeuk-macbookpro.roam.corp.google.com>
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 <49285288-cf99-5f5a-0d1a-c2e0accd8d3d@huawei.com>
 <20181212031749.GF9838@codeaurora.org>
 <0167a499-8479-6be4-946d-4446bd02ff63@huawei.com>
 <20181214075602.GA15236@codeaurora.org>
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 <ad28be8b-361e-550f-50c4-1744e60ff9c5@huawei.com>
 <20181218224700.GD31062@jaegeuk-macbookpro.roam.corp.google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <31efa8cf-95e3-22a2-0c23-9fab9189767f@huawei.com>
Date:   Wed, 19 Dec 2018 11:43:30 +0800
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On 2018/12/19 6:47, Jaegeuk Kim wrote:
> On 12/18, Chao Yu wrote:
>> On 2018/12/14 22:25, Jaegeuk Kim wrote:
>>> On 12/14, Sahitya Tummala wrote:
>>>> On Wed, Dec 12, 2018 at 11:36:08AM +0800, Chao Yu wrote:
>>>>> On 2018/12/12 11:17, Sahitya Tummala wrote:
>>>>>> On Fri, Dec 07, 2018 at 05:47:31PM +0800, Chao Yu wrote:
>>>>>>> On 2018/12/1 4:33, Jaegeuk Kim wrote:
>>>>>>>> On 11/29, Sahitya Tummala wrote:
>>>>>>>>>
>>>>>>>>> On Tue, Nov 27, 2018 at 09:42:39AM +0800, Chao Yu wrote:
>>>>>>>>>> On 2018/11/27 8:30, Jaegeuk Kim wrote:
>>>>>>>>>>> On 11/26, 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.
>>>>>>>>>>>>
>>>>>>>>>>>> Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
>>>>>>>>>>>> ---
>>>>>>>>>>>> v2:
>>>>>>>>>>>> -call evict_inodes() and f2fs_shrink_extent_tree() to cleanup inodes
>>>>>>>>>>>>
>>>>>>>>>>>>  fs/f2fs/f2fs.h     |  1 +
>>>>>>>>>>>>  fs/f2fs/shrinker.c |  2 +-
>>>>>>>>>>>>  fs/f2fs/super.c    | 13 ++++++++++++-
>>>>>>>>>>>>  3 files changed, 14 insertions(+), 2 deletions(-)
>>>>>>>>>>>>
>>>>>>>>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>>>>>>>>> index 1e03197..aaee63b 100644
>>>>>>>>>>>> --- a/fs/f2fs/f2fs.h
>>>>>>>>>>>> +++ b/fs/f2fs/f2fs.h
>>>>>>>>>>>> @@ -3407,6 +3407,7 @@ struct rb_entry *f2fs_lookup_rb_tree_ret(struct rb_root_cached *root,
>>>>>>>>>>>>  bool f2fs_check_rb_tree_consistence(struct f2fs_sb_info *sbi,
>>>>>>>>>>>>  						struct rb_root_cached *root);
>>>>>>>>>>>>  unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink);
>>>>>>>>>>>> +unsigned long __count_extent_cache(struct f2fs_sb_info *sbi);
>>>>>>>>>>>>  bool f2fs_init_extent_tree(struct inode *inode, struct f2fs_extent *i_ext);
>>>>>>>>>>>>  void f2fs_drop_extent_tree(struct inode *inode);
>>>>>>>>>>>>  unsigned int f2fs_destroy_extent_node(struct inode *inode);
>>>>>>>>>>>> diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
>>>>>>>>>>>> index 9e13db9..7e3c13b 100644
>>>>>>>>>>>> --- a/fs/f2fs/shrinker.c
>>>>>>>>>>>> +++ b/fs/f2fs/shrinker.c
>>>>>>>>>>>> @@ -30,7 +30,7 @@ static unsigned long __count_free_nids(struct f2fs_sb_info *sbi)
>>>>>>>>>>>>  	return count > 0 ? count : 0;
>>>>>>>>>>>>  }
>>>>>>>>>>>>  
>>>>>>>>>>>> -static unsigned long __count_extent_cache(struct f2fs_sb_info *sbi)
>>>>>>>>>>>> +unsigned long __count_extent_cache(struct f2fs_sb_info *sbi)
>>>>>>>>>>>>  {
>>>>>>>>>>>>  	return atomic_read(&sbi->total_zombie_tree) +
>>>>>>>>>>>>  				atomic_read(&sbi->total_ext_node);
>>>>>>>>>>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>>>>>>>>>>> index af58b2c..769e7b1 100644
>>>>>>>>>>>> --- a/fs/f2fs/super.c
>>>>>>>>>>>> +++ b/fs/f2fs/super.c
>>>>>>>>>>>> @@ -3016,6 +3016,16 @@ static void f2fs_tuning_parameters(struct f2fs_sb_info *sbi)
>>>>>>>>>>>>  	sbi->readdir_ra = 1;
>>>>>>>>>>>>  }
>>>>>>>>>>>>  
>>>>>>>>>>>> +static void f2fs_cleanup_inodes(struct f2fs_sb_info *sbi)
>>>>>>>>>>>> +{
>>>>>>>>>>>> +	struct super_block *sb = sbi->sb;
>>>>>>>>>>>> +
>>>>>>>>>>>> +	sync_filesystem(sb);
>>>>>>>>>>>
>>>>>>>>>>> This writes another checkpoint, which would not be what this retrial intended.
>>>>>>>>>>
>>>>>>>>>> Actually, checkpoint will not be triggered due to SBI_POR_DOING flag check
>>>>>>>>>> as below:
>>>>>>>>>>
>>>>>>>>>> int f2fs_sync_fs(struct super_block *sb, int sync)
>>>>>>>>>> {
>>>>>>>>>> ...
>>>>>>>>>> 	if (unlikely(is_sbi_flag_set(sbi, SBI_POR_DOING)))
>>>>>>>>>> 		return -EAGAIN;
>>>>>>>>>> ...
>>>>>>>>>> }
>>>>>>>>>>
>>>>>>>>>> And also all dirty data/node won't be persisted due to SBI_POR_DOING flag,
>>>>>>>>>> IIUC.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Thanks Chao for the clarification.
>>>>>>>>>
>>>>>>>>> Hi Jaegeuk,
>>>>>>>>>
>>>>>>>>> Do you still have any further concerns or comments on this patch?
>>>>>>>>
>>>>>>>> Could you try the below first?
>>>>>>>>
>>>>>>>> --  How about adding a condition in f2fs_may_extent_tree() when adding extents?
>>>>>>>> -- Likewise, if (shrinker is not registered) return false;
>>>>>>>>
>>>>>>>> If we can fix what you described directly, I don't want to rely on such the
>>>>>>>> assumptions saying we won't do checkpoint. This flow literally says syncing
>>>>>>>> and evicting cached objects, which opposed to what we'd like to drop all caches
>>>>>>>> and restart fill_super again.
>>>>>>>>
>>>>>>>> Let me consider this as a final resolution.
>>>>>>>
>>>>>>> Jaegeuk,
>>>>>>>
>>>>>>> Still I want to ask, what kind of scenario we have to add retry logic in
>>>>>>> fill_super for? As in android scenario, it must be extreme rare case that
>>>>>>> system runs out-of-memory in boot time...at least, I didn't get any kind of
>>>>>>> report like that.
>>>>>>>
>>>>>> Hi Chao,
>>>>>
>>>>> Hi Sahitya,
>>>>>
>>>>> Thanks for letting me know that, I git-blamed the code, and found the
>>>>> original intention is like what you described:
>>>>>
>>>>> commit ed2e621a95d704e6a4e904cc00524e8cbddda0c2
>>>>> Author: Jaegeuk Kim <jaegeuk@kernel.org>
>>>>> Date:   Fri Aug 8 15:37:41 2014 -0700
>>>>>
>>>>>     f2fs: give a chance to mount again when encountering errors
>>>>>
>>>>>     This patch gives another chance to try mount process when we encounter
>>>>> an error.
>>>>>     This makes an effect on the roll-forward recovery failures as well.
>>>>>
>>>>> But I doubt that if we failed in recovery, maybe there is corruption in
>>>>> this image, would it be better to fail the mount, and let user fsck it and
>>>>> retry the mount? otherwise, the corruption may be expanded...
>>>
>>> The problem was there was no way to recover roll-forward area by fsck. IOWs,
>>> mount was failing all the time. I don't think roll-forward itself can corrupt
>>
>> I got your concern, IMO, if mount fails, it will be better to let user
>> decide how to handle it.
> 
> Roll-forward is not based on user decision, but f2fs does internally. So, I'm

Yup, IMO without roll-forward, data may lose, and posix compliance can be
corrupted, f2fs should do roll-forward internally as possible as it can.

> in doubt we have to ask users on any failed case here.
> I don't catch why we need to revert this which has been landed for a long time.

Actually, what I mean is mount can fail due to different reason, but we
handle it with fixed retry method by dropping recovery, it may be not flexible.

For example, first fill_super fails due to no memory, then second
fill_super runs w/o recovery, if we succeed, we may lose fsynced data. I
don't think it make sense.

Thanks,

> 
>>
>> If mount fails due to:
>>
>> 1) recovery, user can run fsck and/or try disable_roll_forward or
>> norecovery option in another mount;
>> 2) -EINVAL caused by sanity, user can run fsck and retry mount.
>> 3) -ENOMEM caused low memory in system, user can add more memory and retry
>> mount.
>> ...
>>
>> Thanks,
>>
>>> the image more. Please report, if you have any issue on this.>
>>>>>
>>>>
>>>> Hi Jaegeuk,
>>>>
>>>> How do you think about this? If you think it is okay, then I will fix the
>>>> sbi->extent_list corruption issue, by removing the retry logic. Otherwise,
>>>> I will fix it in the extent handling as you have suggested earlier.
>>>
>>> I'd like to keep retry logic, so could you please test what I suggested above?
>>>
>>> Thanks,
>>>
>>>>
>>>> Thanks,
>>>>
>>>>> Thanks,
>>>>>
>>>>>>
>>>>>> In my case, the first boot up has a failure in recovery as below -
>>>>>>
>>>>>> F2FS-fs (mmcblk0p75): find_fsync_dnodes: detect looped node chain, blkaddr:1979471, next:1979472
>>>>>> F2FS-fs (mmcblk0p75): Cannot recover all fsync data errno=-22
>>>>>>
>>>>>> But in the second attempt, retry will be set to false and because of that
>>>>>> recover_fsync_data() is skipped. This helped mount to be successful in
>>>>>> the second attempt. 
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>>>
>>>>>>>>> Thanks,
>>>>>>>>> Sahitya.
>>>>>>>>>
>>>>>>>>>> Thanks,
>>>>>>>>>>
>>>>>>>>>>> How about adding a condition in f2fs_may_extent_tree() when adding extents?
>>>>>>>>>>> Likewise, if (shrinker is not registered) return false;
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>> +	shrink_dcache_sb(sb);
>>>>>>>>>>>> +	evict_inodes(sb);
>>>>>>>>>>>> +	f2fs_shrink_extent_tree(sbi, __count_extent_cache(sbi));
>>>>>>>>>>>> +}
>>>>>>>>>>>> +
>>>>>>>>>>>>  static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>>>>>>>>>>  {
>>>>>>>>>>>>  	struct f2fs_sb_info *sbi;
>>>>>>>>>>>> @@ -3402,6 +3412,8 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>>>>>>>>>>  	 * falls into an infinite loop in f2fs_sync_meta_pages().
>>>>>>>>>>>>  	 */
>>>>>>>>>>>>  	truncate_inode_pages_final(META_MAPPING(sbi));
>>>>>>>>>>>> +	/* cleanup recovery and quota inodes */
>>>>>>>>>>>> +	f2fs_cleanup_inodes(sbi);
>>>>>>>>>>>>  	f2fs_unregister_sysfs(sbi);
>>>>>>>>>>>>  free_root_inode:
>>>>>>>>>>>>  	dput(sb->s_root);
>>>>>>>>>>>> @@ -3445,7 +3457,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>>>>>>>>>>>>  	/* give only one another chance */
>>>>>>>>>>>>  	if (retry) {
>>>>>>>>>>>>  		retry = false;
>>>>>>>>>>>> -		shrink_dcache_sb(sb);
>>>>>>>>>>>>  		goto try_onemore;
>>>>>>>>>>>>  	}
>>>>>>>>>>>>  	return err;
>>>>>>>>>>>> -- 
>>>>>>>>>>>> Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
>>>>>>>>>>>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
>>>>>>>>>>>
>>>>>>>>>>> .
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> -- 
>>>>>>>>> --
>>>>>>>>> Sent by a consultant of the Qualcomm Innovation Center, Inc.
>>>>>>>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
>>>>>>>>
>>>>>>>> .
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>> -- 
>>>> --
>>>> Sent by a consultant of the Qualcomm Innovation Center, Inc.
>>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
>>>
>>> .
>>>
> 
> .
>