Date:   Tue, 18 Dec 2018 14:47:00 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     Sahitya Tummala <stummala@...eaurora.org>,
        linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] f2fs: fix sbi->extent_list corruption issue

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@...eaurora.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@...nel.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
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.

> 
> 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.
> > 
> > .
> > 

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