linux-kernel - Re: [PATCH 2/2] f2fs: fix the inconsistent state of data pages

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Date:	Wed, 15 May 2013 13:04:08 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH 2/2] f2fs: fix the inconsistent state of data pages

2013/5/15, Jaegeuk Kim <jaegeuk.kim@...sung.com>:
> In get_lock_data_page, if there is a data race between get_dnode_of_data
> for
> node and grab_cache_page for data, f2fs is able to face with the following
> BUG_ON(dn.data_blkaddr == NEW_ADDR).
>
> kernel BUG at /home/zeus/f2fs_test/src/fs/f2fs/data.c:251!
>  [<ffffffffa044966c>] get_lock_data_page+0x1ec/0x210 [f2fs]
> Call Trace:
>  [<ffffffffa043b089>] f2fs_readdir+0x89/0x210 [f2fs]
>  [<ffffffff811a0920>] ? fillonedir+0x100/0x100
>  [<ffffffff811a0920>] ? fillonedir+0x100/0x100
>  [<ffffffff811a07f8>] vfs_readdir+0xb8/0xe0
>  [<ffffffff811a0b4f>] sys_getdents+0x8f/0x110
>  [<ffffffff816d7999>] system_call_fastpath+0x16/0x1b
>
> This bug is able to be occurred when the block address of the data block is
> changed after f2fs_put_dnode().
> In order to avoid that, this patch fixes the lock order of node and data
> blocks in which the node block lock is covered by the data block lock.
>
> Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
> ---
>  fs/f2fs/data.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 91ff93b..05fb5c6 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -233,18 +233,23 @@ struct page *get_lock_data_page(struct inode *inode,
> pgoff_t index)
>  	struct page *page;
>  	int err;
>
> +repeat:
> +	page = grab_cache_page(mapping, index);
> +	if (!page)
> +		return ERR_PTR(-ENOMEM);
> +
>  	set_new_dnode(&dn, inode, NULL, NULL, 0);
>  	err = get_dnode_of_data(&dn, index, LOOKUP_NODE);
> -	if (err)
> +	if (err) {
> +		f2fs_put_page(page, 1);
>  		return ERR_PTR(err);
> +	}
>  	f2fs_put_dnode(&dn);
>
> -	if (dn.data_blkaddr == NULL_ADDR)
> +	if (dn.data_blkaddr == NULL_ADDR) {
> +		f2fs_put_page(page, 1);
>  		return ERR_PTR(-ENOENT);
> -repeat:
> -	page = grab_cache_page(mapping, index);
> -	if (!page)
> -		return ERR_PTR(-ENOMEM);
> +	}
>
>  	if (PageUptodate(page))
>  		return page;
Is there no need to move PageUptodate condition checking to
grab_cache_page next ?

Thanks.
> --
> 1.8.1.3.566.gaa39828
>
> --
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