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

[Chao Yu <yuchao0@huawei.com>]

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.

> 
> 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@kernel.org>
> Date: Fri, 4 Jan 2019 12:29:00 -0800
> Subject: [PATCH] f2fs: sync filesystem after roll-forward recovery

You mean android kernel mainline?

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@codeaurora.org>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  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);
>