linux-kernel - Re: [PATCH -next 1/2] xfs: simplify if-else condition in xfs_validate_new

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Message-ID: <Yw4qd38m++Wg2uXQ@magnolia>
Date:   Tue, 30 Aug 2022 08:19:19 -0700
From:   "Darrick J. Wong" <djwong@...nel.org>
To:     Zeng Heng <zengheng4@...wei.com>
Cc:     linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next 1/2] xfs: simplify if-else condition in
 xfs_validate_new_dalign

On Tue, Aug 30, 2022 at 09:39:38PM +0800, Zeng Heng wrote:
> "else" is not generally useful after a return,
> so remove them which makes if condition a bit
> more clear.
> 
> There is no logical changes.
> 
> Signed-off-by: Zeng Heng <zengheng4@...wei.com>

Yep.
Reviewed-by: Darrick J. Wong <djwong@...nel.org>

--D

> ---
>  fs/xfs/xfs_mount.c | 38 ++++++++++++++++++++------------------
>  1 file changed, 20 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index f10c88cee116..e8bb3c2e847e 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -300,26 +300,28 @@ xfs_validate_new_dalign(
>  	"alignment check failed: sunit/swidth vs. blocksize(%d)",
>  			mp->m_sb.sb_blocksize);
>  		return -EINVAL;
> -	} else {
> -		/*
> -		 * Convert the stripe unit and width to FSBs.
> -		 */
> -		mp->m_dalign = XFS_BB_TO_FSBT(mp, mp->m_dalign);
> -		if (mp->m_dalign && (mp->m_sb.sb_agblocks % mp->m_dalign)) {
> -			xfs_warn(mp,
> -		"alignment check failed: sunit/swidth vs. agsize(%d)",
> -				 mp->m_sb.sb_agblocks);
> -			return -EINVAL;
> -		} else if (mp->m_dalign) {
> -			mp->m_swidth = XFS_BB_TO_FSBT(mp, mp->m_swidth);
> -		} else {
> -			xfs_warn(mp,
> -		"alignment check failed: sunit(%d) less than bsize(%d)",
> -				 mp->m_dalign, mp->m_sb.sb_blocksize);
> -			return -EINVAL;
> -		}
>  	}
>  
> +	/*
> +	 * Convert the stripe unit and width to FSBs.
> +	 */
> +	mp->m_dalign = XFS_BB_TO_FSBT(mp, mp->m_dalign);
> +	if (mp->m_dalign && (mp->m_sb.sb_agblocks % mp->m_dalign)) {
> +		xfs_warn(mp,
> +	"alignment check failed: sunit/swidth vs. agsize(%d)",
> +			mp->m_sb.sb_agblocks);
> +		return -EINVAL;
> +	}
> +
> +	if (!mp->m_dalign) {
> +		xfs_warn(mp,
> +	"alignment check failed: sunit(%d) less than bsize(%d)",
> +			mp->m_dalign, mp->m_sb.sb_blocksize);
> +		return -EINVAL;
> +	}
> +
> +	mp->m_swidth = XFS_BB_TO_FSBT(mp, mp->m_swidth);

I think this reorganization of the if test logic is correct, but I
really wish this unit abuse ("m_swidth is a BB for short periods of time
and fsblock everywhere else") would get fixed to simplify analysis and
prevent us from stumbling over things like that some time later.

So for this change,
Reviewed-by: Darrick J. Wong <djwong@...nel.org>

But I would be very happy to see some tripping hazard removal. ;)

--D

> +
>  	if (!xfs_has_dalign(mp)) {
>  		xfs_warn(mp,
>  "cannot change alignment: superblock does not support data alignment");
> -- 
> 2.25.1
>