linux-kernel - Re: [PATCH v6 3/4] scatterlist: add sgl_compare

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Date:   Tue, 19 Jan 2021 12:50:15 +0100
From:   David Disseldorp <ddiss@...e.de>
To:     Douglas Gilbert <dgilbert@...erlog.com>
Cc:     linux-scsi@...r.kernel.org, linux-block@...r.kernel.org,
        target-devel@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, martin.petersen@...cle.com,
        jejb@...ux.vnet.ibm.com, bostroesser@...il.com, bvanassche@....org,
        jgg@...pe.ca
Subject: Re: [PATCH v6 3/4] scatterlist: add sgl_compare_sgl() function

On Mon, 18 Jan 2021 20:04:20 -0500, Douglas Gilbert wrote:

> >> +bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip,
> >> +		     struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip,
> >> +		     size_t n_bytes);
> >> +
> >> +bool sgl_compare_sgl_idx(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip,
> >> +			 struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip,
> >> +			 size_t n_bytes, size_t *miscompare_idx);  
> > 
> > 
> > This patch looks good and works fine as a replacement for
> > compare_and_write_do_cmp(). One minor suggestion would be to name it
> > sgl_equal() or similar, to perhaps better reflect the bool return and
> > avoid memcmp() confusion. Either way:
> > Reviewed-by: David Disseldorp <ddiss@...e.de>  
> 
> Thanks. NVMe calls the command that does this Compare and SCSI uses
> COMPARE AND WRITE (and VERIFY(BYTCHK=1) ) but "equal" is fine with me.
> There will be another patchset version (at least) so there is time
> to change.
> 
> Do you want:
>    - sgl_equal(...), or
>    - sgl_equal_sgl(...) ?

I'd probably prefer the former as it's shorter, but I don't feel
strongly about it. The latter would make sense if you expect sgl compare
helpers for other buffer types.

Cheers, David