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

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Date:   Tue, 11 Oct 2016 15:19:03 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...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 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.

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