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From: Jan Kara <jack@suse.cz>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
	jack@suse.cz, bart.vanassche@wdc.com, ming.lei@redhat.com,
	rjw@rjwysocki.net, mguzik@redhat.com, linux-pm@vger.kernel.org,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] fs: fix corner case race on freeze_bdev() when sb disappears
Date: Thu, 3 May 2018 17:02:17 +0200	[thread overview]
Message-ID: <20180503150217.ywu2cuxjbsgr47a6@quack2.suse.cz> (raw)
In-Reply-To: <20180420235904.27496-4-mcgrof@kernel.org>

On Fri 20-04-18 16:59:04, Luis R. Rodriguez wrote:
> freeze_bdev() will bail but leave the bd_fsfreeze_count incremented
> if the get_active_super() does not find the superblock on our
> super_blocks list to match.
> 
> This issue has been present since v2.6.29 during the introduction of the
> ioctl_fsfreeze() and ioctl_fsthaw() via commit fcccf502540e3 ("filesystem
> freeze: implement generic freeze feature").
> 
> I am not aware of any existing races which have triggered this
> situation, however, if it does trigger it could mean leaving a
> superblock with bd_fsfreeze_count always positive.
> 
> Fixes: fcccf502540e3 ("filesystem freeze: implement generic freeze feature")
> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>

Looks good to me. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  fs/block_dev.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index b54966679833..7a532aa58c07 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -507,8 +507,10 @@ struct super_block *freeze_bdev(struct block_device *bdev)
>  	}
>  
>  	sb = get_active_super(bdev);
> -	if (!sb)
> +	if (!sb) {
> +		bdev->bd_fsfreeze_count--;
>  		goto out;
> +	}
>  	if (sb->s_op->freeze_super)
>  		error = sb->s_op->freeze_super(sb);
>  	else
> -- 
> 2.16.3
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

  reply	other threads:[~2018-05-03 15:02 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-20 23:59 [PATCH 0/3] fs: minor fs thaw fixes and adjustments Luis R. Rodriguez
2018-04-20 23:59 ` [PATCH 1/3] fs: move documentation for thaw_super() where appropriate Luis R. Rodriguez
2018-04-21  0:01   ` Bart Van Assche
2018-04-21  0:07     ` Luis R. Rodriguez
2018-04-21  0:09       ` Randy Dunlap
2018-05-03 14:53   ` Jan Kara
2018-04-20 23:59 ` [PATCH 2/3] fs: make thaw_super_locked() really just a helper Luis R. Rodriguez
2018-05-03 15:07   ` Jan Kara
2018-04-20 23:59 ` [PATCH 3/3] fs: fix corner case race on freeze_bdev() when sb disappears Luis R. Rodriguez
2018-05-03 15:02   ` Jan Kara [this message]
2018-04-21  0:02 ` [PATCH 0/3] fs: minor fs thaw fixes and adjustments Luis R. Rodriguez

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