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Subject: Re: [PATCH v2] f2fs: fix sbi->extent_list corruption issue
To:     Jaegeuk Kim <jaegeuk@kernel.org>,
        Sahitya Tummala <stummala@codeaurora.org>
CC:     <linux-f2fs-devel@lists.sourceforge.net>,
        <linux-kernel@vger.kernel.org>
References: <1543207640-31033-1-git-send-email-stummala@codeaurora.org>
 <20181127003050.GG55960@jaegeuk-macbookpro.roam.corp.google.com>
 <fc8c38f6-a039-7b63-d25c-966b0d4396d8@huawei.com>
 <20181129033239.GE9838@codeaurora.org>
 <20181130203339.GB71781@jaegeuk-macbookpro.roam.corp.google.com>
From:   Chao Yu <yuchao0@huawei.com>
Message-ID: <49285288-cf99-5f5a-0d1a-c2e0accd8d3d@huawei.com>
Date:   Fri, 7 Dec 2018 17:47:31 +0800
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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.

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.
> 
> .
>