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Date:   Fri, 14 Dec 2018 06:25:37 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Sahitya Tummala <stummala@codeaurora.org>
Cc:     Chao Yu <yuchao0@huawei.com>,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] f2fs: fix sbi->extent_list corruption issue
Message-ID: <20181214142537.GA75922@jaegeuk-macbookpro.roam.corp.google.com>
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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
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.