linux-kernel - Re: [PATCH 6/6] lib/scatterlist: Drop order argument from sgl_free_n

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Message-ID: <b07f8f6b-4264-d1d1-1e14-b22932130ac4@ursulin.net>
Date:   Thu, 8 Mar 2018 17:06:36 +0000
From:   Tvrtko Ursulin <tursulin@...ulin.net>
To:     Bart Van Assche <Bart.VanAssche@....com>,
        "James.Bottomley@...senPartnership.com" 
        <James.Bottomley@...senPartnership.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Cc:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "tvrtko.ursulin@...el.com" <tvrtko.ursulin@...el.com>,
        "hare@...e.com" <hare@...e.com>,
        "jthumshirn@...e.de" <jthumshirn@...e.de>,
        "target-devel@...r.kernel.org" <target-devel@...r.kernel.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "nab@...ux-iscsi.org" <nab@...ux-iscsi.org>
Subject: Re: [PATCH 6/6] lib/scatterlist: Drop order argument from
 sgl_free_n_order


On 08/03/18 15:56, Bart Van Assche wrote:
> On Thu, 2018-03-08 at 07:59 +0000, Tvrtko Ursulin wrote:
>> However there is a different bug in my patch relating to the last entry
>> which can have shorter length from the rest. So get_order on the last
>> entry is incorrect - I have to store the deduced order and carry it over.
> 
> Will that work if there is only one entry in the list and if it is a short
> entry?

Yeah, needs more work. I especially don't like that case (as in any 
other with a final short chunk) wasting memory. So it would need more 
refactoring to make it possible.

It did work in my internal tree where sgl_alloc_order was extended to 
become sgl_alloc_order_min_max, and as such uses a smaller order for 
smaller chunks.

This patch can be dropped for now but the earlier ones are still valid I 
think. On those one I think we have some opens on how to proceed so if 
you could reply there, where applicable, that would be great.

Regards,

Tvrtko