linux-kernel - Re: [PATCH] f2fs: Return the errno to the caller to avoid using a wrong page

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Message-ID: <20160525165438.GB47096@jaegeuk.gateway>
Date:	Wed, 25 May 2016 09:54:38 -0700
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	Yunlong Song <yunlong.song@...wei.com>
Cc:	cm224.lee@...sung.com, yuchao0@...wei.com, chao@...nel.org,
	sylinux@....com, bintian.wang@...wei.com, houpengyang@...wei.com,
	heyunlei@...wei.com, liushuoran@...wei.com, shiguojun@...wei.com,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: Return the errno to the caller to avoid using a
 wrong page

Hi Yunlong,

Do we have a bug report in terms of this?

Thanks,

On Wed, May 25, 2016 at 09:01:01PM +0800, Yunlong Song wrote:
> Commit aaf9607516ed38825268515ef4d773289a44f429 ("f2fs: check node page
> contents all the time") pointed out that "sometimes it was reported that
> its contents was missing", so it checks the page's mapping and contents.
> When "nid != nid_of_node(page)", ERR_PTR(-EIO) will be returned to the
> caller. However, commit e1c51b9f1df2f9efc2ec11488717e40cd12015f9 ("f2fs:
> clean up node page updating flow") moves "nid != nid_of_node(page)" test
> to "f2fs_bug_on(sbi, nid != nid_of_node(page))", this will return a
> wrong page to the caller when F2FS_CHECK_FS is off when "sometimes it
> was reported that its contents was missing" happens.
> 
> This patch restores to check node page contents all the time, and
> returns the errno to make the caller known something is wrong and avoid
> to use the page. This patch also moves f2fs_bug_on to its proper location.
> 
> Signed-off-by: Yunlong Song <yunlong.song@...wei.com>
> ---
>  fs/f2fs/node.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 1f21aae..4b04af4 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1140,16 +1140,16 @@ repeat:
>  	if (err < 0) {
>  		f2fs_put_page(page, 1);
>  		return ERR_PTR(err);
> -	} else if (err == LOCKED_PAGE) {
> -		goto page_hit;
> +	} else if (err != LOCKED_PAGE) {
> +		lock_page(page);
>  	}
>  
>  	if (parent)
>  		ra_node_pages(parent, start + 1, MAX_RA_NODE);
>  
> -	lock_page(page);
> -
> -	if (unlikely(!PageUptodate(page))) {
> +	if (unlikely(!PageUptodate(page) || nid != nid_of_node(page))) {
> +		f2fs_bug_on(sbi, 1);
> +		ClearPageUptodate(page);
>  		f2fs_put_page(page, 1);
>  		return ERR_PTR(-EIO);
>  	}
> @@ -1157,8 +1157,6 @@ repeat:
>  		f2fs_put_page(page, 1);
>  		goto repeat;
>  	}
> -page_hit:
> -	f2fs_bug_on(sbi, nid != nid_of_node(page));
>  	return page;
>  }
>  
> -- 
> 1.8.5.2