Re: [PATCH 1/2] f2fs: fix sbi->extent_list corruption issue

[Chao Yu]

On 2018/11/23 11:42, Sahitya Tummala wrote:
> On Thu, Nov 22, 2018 at 04:11:07AM -0800, Jaegeuk Kim wrote:
>> On 11/22, Chao Yu wrote:
>>> On 2018/11/22 18:59, 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 the extent tree of those recovered files
>>>> before freeing up sbi and before next retry.
>>>
>>> Would it be more clear to call shrink_dcache_sb earlier to invalid all
>>> inodes and call f2fs_shrink_extent_tree release cached entries and trees in
>>> error path?
>>
>> Agreed.
>>
> I have tried doing shrink_dcache_sb() earlier but that doesn't call
> f2fs_shrink_extent_tree(). So I have moved f2fs_join_shrinker() earlier and 
> tried calling f2fs_leave_shrinker() in the error path. That helps to clean up
> the cached extent nodes. However, I see that extent tree is left intact for

I didn't get it, you mean, in error path, after we call shrink_dcache_sb &
f2fs_leave_shrinker, for those recovered files, their extent nodes were
evicted, but their extent trees are still in cache?

> those recovered files, which should not be a problem as it gets freed as part
> of next umount/rm. Only one small problem I see with this is - during rm/umount when
> those previoulsy recovered files are being evicted, extent tree memory gets
> free'd but the counter sbi->total_ext_tree gets invalid as these recovered
> files are not present as part of current sbi->extent_tree_root. So i have come
> up with this patch below to fix this. Let me know if this looks good?
> 
> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
> index 1cb0fcc..3e4801e 100644
> --- a/fs/f2fs/extent_cache.c
> +++ b/fs/f2fs/extent_cache.c
> @@ -654,9 +654,9 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
>  		}
>  		f2fs_bug_on(sbi, atomic_read(&et->node_cnt));
>  		list_del_init(&et->list);
> -		radix_tree_delete(&sbi->extent_tree_root, et->ino);
> +		if (radix_tree_delete(&sbi->extent_tree_root, et->ino))
> +			atomic_dec(&sbi->total_ext_tree);
>  		kmem_cache_free(extent_tree_slab, et);
> -		atomic_dec(&sbi->total_ext_tree);
>  		atomic_dec(&sbi->total_zombie_tree);
>  		tree_cnt++;
>  
> @@ -767,7 +767,8 @@ void f2fs_destroy_extent_tree(struct inode *inode)
>  	/* delete extent tree entry in radix tree */
>  	mutex_lock(&sbi->extent_tree_lock);
>  	f2fs_bug_on(sbi, atomic_read(&et->node_cnt));
> -	radix_tree_delete(&sbi->extent_tree_root, inode->i_ino);
> +	if (radix_tree_delete(&sbi->extent_tree_root, inode->i_ino))
> +		atomic_dec(&sbi->total_ext_tree);
>  	kmem_cache_free(extent_tree_slab, et);
>  	atomic_dec(&sbi->total_ext_tree);
>  	mutex_unlock(&sbi->extent_tree_lock);
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index af58b2c..3e5588f 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -3295,6 +3295,7 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>  	if (err)
>  		goto free_root_inode;
>  
> +	f2fs_join_shrinker(sbi);
>  #ifdef CONFIG_QUOTA
>  	/* Enable quota usage during mount */
>  	if (f2fs_sb_has_quota_ino(sb) && !f2fs_readonly(sb)) {
> @@ -3379,8 +3380,6 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
>  			sbi->valid_super_block ? 1 : 2, err);
>  	}
>  
> -	f2fs_join_shrinker(sbi);
> -
>  	f2fs_tuning_parameters(sbi);
>  
>  	f2fs_msg(sbi->sb, KERN_NOTICE, "Mounted with checkpoint version = %llx",
> @@ -3402,6 +3401,8 @@ 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));
> +	shrink_dcache_sb(sb);
> +	f2fs_leave_shrinker(sbi);

Why not just calling f2fs_shrink_extent_tree(sbi, __count_extent_cache(sbi)); ?

Thanks,

>  	f2fs_unregister_sysfs(sbi);
>  free_root_inode:
>  	dput(sb->s_root);
> @@ -3445,7 +3446,6 @@ 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;
>