linux-kernel - Re: [PATCH] lib/scatterlist: Fix to calculate the last

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Message-ID: <f8168426-def6-333a-53b4-8947341b84c4@deltatee.com>
Date:   Mon, 9 Jan 2023 11:08:44 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Yishai Hadas <yishaih@...dia.com>, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org, linux-mm@...ck.org, jgg@...dia.com,
        axboe@...nel.dk
Cc:     hch@....de, alex.williamson@...hat.com, leonro@...dia.com,
        maorg@...dia.com
Subject: Re: [PATCH] lib/scatterlist: Fix to calculate the last_pg properly



On 2023-01-09 07:47, Yishai Hadas wrote:
> The last_pg is wrong, it is actually the first page of the last
> scatterlist element. To get the last page of the last scatterlist
> element we have to add prv->length. So it is checking mergability
> against the wrong page, Further, a SG element is not guaranteed to end
> on a page boundary, so we have to check the sub page location also for
> merge eligibility.
> 
> Fix the above by checking physical contiguity, compute the actual last
> page and then call pages_are_mergable().
> 
> Fixes: 1567b49d1a40 ("lib/scatterlist: add check when merging zone device pages")
> Reported-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Yishai Hadas <yishaih@...dia.com>

Looks right by my eye, thanks.

Reviewed-by: Logan Gunthorpe <logang@...tatee.com>

Logan