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Date: Mon, 23 May 2016 07:51:16 -0700
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH] xfs_repair: further improvement on secondary superblock
	search method
Message-ID: <20160523145116.GE9319@infradead.org>
References: <1463085496-17919-1-git-send-email-billodo@redhat.com>
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To: Bill O'Donnell <billodo@redhat.com>
Cc: xfs@oss.sgi.com

On Thu, May 12, 2016 at 03:38:16PM -0500, Bill O'Donnell wrote:
> +verify_sb_blocksize(xfs_sb_t *sb)
> +{
> +	__uint32_t	bsize;
> +	int		i;
> +
> +	/* check to make sure blocksize is legal 2^N, 9 <= N <= 16 */
> +	if (sb->sb_blocksize == 0)
> +		return(XR_BAD_BLOCKSIZE);
> +
> +	bsize = 1;
> +
> +	for (i = 0; bsize < sb->sb_blocksize &&
> +		i < sizeof(sb->sb_blocksize) * NBBY; i++)
> +		bsize <<= 1;
> +
> +	if (i < XFS_MIN_BLOCKSIZE_LOG || i > XFS_MAX_BLOCKSIZE_LOG)
> +		return(XR_BAD_BLOCKSIZE);
> +
> +	/* check sb blocksize field against sb blocklog field */
> +	if (i != sb->sb_blocklog)
> +		return(XR_BAD_BLOCKLOG);

Couldn't we do this much simpler?

	if (sb->sb_blocksize == 0)
		return XR_BAD_BLOCKSIZE;
	if (sb->sb_blocksize != (1 << sb->sb_blocklog))
		return XR_BAD_BLOCKLOG;
	if (sb->sb_blocklog < XFS_MIN_BLOCKSIZE_LOG ||
	    sb->sb_blocklog > XFS_MAX_BLOCKSIZE_LOG)
		return XR_BAD_BLOCKLOG;

>  	/*
> +	 * Attempt to find secondary sb with a coarse approach,
> +	 * first trying agblocks and blocksize read from sb, providing
> +	 * they're sane.
>  	 */
> +	if (verify_sb_blocksize(rsb) == 0) {
> +		skip = rsb->sb_agblocks * rsb->sb_blocksize;
> +		if ((skip >= XFS_AG_MIN_BYTES) && (skip <= XFS_AG_MAX_BYTES))

no need for the inner braces here.

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