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Date:   Tue, 28 Nov 2023 22:34:09 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Dave Chinner <david@fromorbit.com>
Cc:     Jiachen Zhang <zhangjiachen.jaycee@bytedance.com>,
        Chandan Babu R <chandan.babu@oracle.com>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Dave Chinner <dchinner@redhat.com>,
        Allison Henderson <allison.henderson@oracle.com>,
        Zhang Tianci <zhangtianci.1997@bytedance.com>,
        Brian Foster <bfoster@redhat.com>, Ben Myers <bpm@sgi.com>,
        linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org,
        xieyongji@bytedance.com, me@jcix.top
Subject: Re: [PATCH 2/2] xfs: update dir3 leaf block metadata after swap
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References: <20231128053202.29007-1-zhangjiachen.jaycee@bytedance.com>
 <20231128053202.29007-3-zhangjiachen.jaycee@bytedance.com>
 <ZWZ0qGWpBTW6Iynt@dread.disaster.area>
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On Wed, Nov 29, 2023 at 10:15:52AM +1100, Dave Chinner wrote:
> > +	/*
> > +	 * Update the moved block's blkno if it's a dir3 leaf block
> > +	 */
> > +	if (dead_info->magic == cpu_to_be16(XFS_DIR3_LEAF1_MAGIC) ||
> > +	    dead_info->magic == cpu_to_be16(XFS_DIR3_LEAFN_MAGIC) ||
> > +	    dead_info->magic == cpu_to_be16(XFS_ATTR3_LEAF_MAGIC)) {
> 
> a.k.a.
> 
> 	if (xfs_has_crc(mp)) {
> 
> i.e. this is not specific to the buffer type being processed, it's
> specific to v4 vs v5 on-disk format. Hence it's a fs-feature check,
> not a block magic number check.

We have these magic based checks in quite a few places right now,
so I'm not surprised that Jiachen picked it up from there..