From: Chao Yu <chao2.yu@samsung.com>
To: "'Jaegeuk Kim'" <jaegeuk@kernel.org>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net
References: <1439887589-35190-1-git-send-email-jaegeuk@kernel.org>
 <1439887589-35190-5-git-send-email-jaegeuk@kernel.org>
In-reply-to: <1439887589-35190-5-git-send-email-jaegeuk@kernel.org>
Subject: RE: [f2fs-dev] [PATCH 5/5] f2fs: check the node block address of newly
	allocated nid
Date: Thu, 20 Aug 2015 17:12:03 +0800
Message-id: <01bb01d0db28$61844ea0$248cebe0$@samsung.com>
MIME-version: 1.0
Content-type: text/plain; charset=us-ascii
Content-transfer-encoding: 7bit
Thread-index: AQMbK+U27TEaBuzOkuL9EYWgZcyS+gL3ywKSm2gwOMA=
Content-language: zh-cn
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2366
Lines: 73

Hi Jaegeuk,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> Sent: Tuesday, August 18, 2015 4:46 PM
> To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> linux-f2fs-devel@lists.sourceforge.net
> Cc: Jaegeuk Kim
> Subject: [f2fs-dev] [PATCH 5/5] f2fs: check the node block address of newly allocated nid
> 
> This patch adds a routine which checks the block address of newly allocated nid.
> If an nid has already allocated by other thread due to subtle data races, it
> will result in filesystem corruption.
> So, it needs to check whether its block address was already allocated or not
> in prior to nid allocation as the last chance.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/node.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 3cc32b8..6bef5a2 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1573,6 +1573,8 @@ retry:
> 
>  	/* We should not use stale free nids created by build_free_nids */
>  	if (nm_i->fcnt && !on_build_free_nids(nm_i)) {
> +		struct node_info ni;
> +
>  		f2fs_bug_on(sbi, list_empty(&nm_i->free_nid_list));
>  		list_for_each_entry(i, &nm_i->free_nid_list, list)
>  			if (i->state == NID_NEW)
> @@ -1583,6 +1585,13 @@ retry:
>  		i->state = NID_ALLOC;
>  		nm_i->fcnt--;
>  		spin_unlock(&nm_i->free_nid_list_lock);
> +
> +		/* check nid is allocated already */
> +		get_node_info(sbi, *nid, &ni);
> +		if (ni.blk_addr != NULL_ADDR) {

I didn't get it, why free nid is with non-NULL blkaddr?
Could you please explain more about this?

> +			alloc_nid_done(sbi, *nid);

Will another thread call alloc_nid_done too, making this free nid being
released again?

Thanks,

> +			goto retry;
> +		}
>  		return true;
>  	}
>  	spin_unlock(&nm_i->free_nid_list_lock);
> --
> 2.1.1
> 
> 
> ------------------------------------------------------------------------------
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/