linux-kernel - Re: [PATCH 1/8] f2fs: clear nlink if fail to add

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Date:   Wed, 12 Oct 2016 23:24:28 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <yuchao0@...wei.com>
Subject: Re: [PATCH 1/8] f2fs: clear nlink if fail to add_link

Hi Jaegeuk,

On 2016/10/12 6:19, Jaegeuk Kim wrote:
> Hi Chao,
> 
> On Tue, Oct 11, 2016 at 10:56:59PM +0800, Chao Yu wrote:
>> From: Chao Yu <yuchao0@...wei.com>
>>
>> We don't need to keep incomplete created inode in cache, so if we fail to
>> add link into directory during new inode creation, it's better to set
>> nlink of inode to zero, then we can evict inode immediately. Otherwise
>> release of nid belong to inode will be delayed until inode cache is being
>> shrunk, it may cause a seemingly endless loop while allocating free nids
>> in time of testing generic/269 case of fstest suit.
>>
>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>> ---
>>  fs/f2fs/inode.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>> index d736989..34ae03c 100644
>> --- a/fs/f2fs/inode.c
>> +++ b/fs/f2fs/inode.c
>> @@ -384,6 +384,8 @@ retry:
>>  		f2fs_lock_op(sbi);
>>  		err = remove_inode_page(inode);
>>  		f2fs_unlock_op(sbi);
>> +		if (err == -ENOENT)
>> +			err = 0;
>>  	}
>>  
>>  	/* give more chances, if ENOMEM case */
>> @@ -424,6 +426,12 @@ void handle_failed_inode(struct inode *inode)
>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>  	struct node_info ni;
>>  
>> +	/*
>> +	 * clear nlink of inode in order to release resource of inode
>> +	 * immediately.
>> +	 */
>> +	clear_nlink(inode);
> 
> We must call update_inode_page() here to avoid kernel panic.
> Otherwise, this inode is kept in the gdirty list, resulting in kernel panic
> when flushg dirty inodes, since it was already evicted.

Thanks for fixing this, is this panic produced with fault injection?

Thanks,

> 
> I fixed this and started a round of tests.
> 
> Thanks,
> 
>> +
>>  	/* don't make bad inode, since it becomes a regular file. */
>>  	unlock_new_inode(inode);
>>  
>> -- 
>> 2.10.1