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Message-id: <01bb01d0db28$61844ea0$248cebe0$@samsung.com>
Date: Thu, 20 Aug 2015 17:12:03 +0800
From: Chao Yu <chao2.yu@...sung.com>
To: 'Jaegeuk Kim' <jaegeuk@...nel.org>, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
Subject: RE: [f2fs-dev] [PATCH 5/5] f2fs: check the node block address of newly
allocated nid
Hi Jaegeuk,
> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@...nel.org]
> Sent: Tuesday, August 18, 2015 4:46 PM
> To: linux-kernel@...r.kernel.org; linux-fsdevel@...r.kernel.org;
> linux-f2fs-devel@...ts.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@...nel.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
>
>
> ------------------------------------------------------------------------------
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