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Date:   Mon, 25 Mar 2019 09:55:17 -0500
From:   Eric Sandeen <esandeen@...hat.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>,
        xfs <linux-xfs@...r.kernel.org>
Cc:     fstests <fstests@...r.kernel.org>, Eryu Guan <guaneryu@...il.com>,
        linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] xfs: prohibit fstrim in norecovery mode

On 3/22/19 7:37 PM, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@...cle.com>
> 
> The xfs fstrim implementation uses the free space btrees to find free
> space that can be discarded.  If we haven't recovered the log, the bnobt
> will be stale and we absolutely *cannot* use stale metadata to zap the
> underlying storage.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> ---
>  fs/xfs/xfs_discard.c |    8 ++++++++
>  1 file changed, 8 insertions(+)

Yikes...

Looks good to me (I briefly thought about a norecovery mount with a clean log,
but then decided I didn't care about that)

Reviewed-by: Eric Sandeen <sandeen@...hat.com>

> diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c
> index 93f07edafd81..9ee2a7d02e70 100644
> --- a/fs/xfs/xfs_discard.c
> +++ b/fs/xfs/xfs_discard.c
> @@ -161,6 +161,14 @@ xfs_ioc_trim(
>  		return -EPERM;
>  	if (!blk_queue_discard(q))
>  		return -EOPNOTSUPP;
> +
> +	/*
> +	 * We haven't recovered the log, so we cannot use our bnobt-guided
> +	 * storage zapping commands.
> +	 */
> +	if (mp->m_flags & XFS_MOUNT_NORECOVERY)
> +		return -EROFS;
> +
>  	if (copy_from_user(&range, urange, sizeof(range)))
>  		return -EFAULT;
>  
> 

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