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Subject: Re: [PATCH V11 1/8] block, bfq: split sync bfq_queues on a
 per-actuator basis
From:   Paolo Valente <paolo.valente@linaro.org>
In-Reply-To: <017f3dbd-4586-490a-2f21-948586391515@opensource.wdc.com>
Date:   Thu, 22 Dec 2022 15:37:28 +0100
Cc:     Jens Axboe <axboe@kernel.dk>,
        linux-block <linux-block@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Arie van der Hoeven <arie.vanderhoeven@seagate.com>,
        Rory Chen <rory.c.chen@seagate.com>,
        Glen Valante <glen.valante@linaro.org>,
        Gabriele Felici <felicigb@gmail.com>,
        Carmine Zaccagnino <carmine@carminezacc.com>
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Message-Id: <E6644B35-D439-4DB8-93DC-EF77D580FCA0@linaro.org>
References: <20221220095013.55803-1-paolo.valente@linaro.org>
 <20221220095013.55803-2-paolo.valente@linaro.org>
 <8a49432d-642f-cd58-8e4d-2b320aef5edd@opensource.wdc.com>
 <D429FA01-9510-41FF-AD85-F74EB8AD171F@linaro.org>
 <017f3dbd-4586-490a-2f21-948586391515@opensource.wdc.com>
To:     Damien Le Moal <damien.lemoal@opensource.wdc.com>
Precedence: bulk


> Il giorno 21 dic 2022, alle ore 13:27, Damien Le Moal =
<damien.lemoal@opensource.wdc.com> ha scritto:
>=20
> On 2022/12/21 19:27, Paolo Valente wrote:
>>=20
>>=20
>>> Il giorno 21 dic 2022, alle ore 01:46, Damien Le Moal =
<damien.lemoal@opensource.wdc.com> ha scritto:
>>>=20
>>>=20
>>> [...]
>>>=20
>>>> -static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync)
>>>> +static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync,
>>>> +			      unsigned int actuator_idx)
>>>> {
>>>> -	struct bfq_queue *bfqq =3D bic_to_bfqq(bic, is_sync);
>>>> +	struct bfq_queue *bfqq =3D bic_to_bfqq(bic, is_sync, =
actuator_idx);
>>>> 	struct bfq_data *bfqd;
>>>>=20
>>>> 	if (bfqq)
>>>=20
>>> With your current bic_to_bfqq() implementation, you will *never* get =
NULL as a
>>> return value.
>>=20
>> I'm afraid this is not true.  A bic is associated with a sync and an
>> async queue, or with both.  So, in the hunk above, bic_to_bfqq =
returns
>> NULL if:
>> - either the bic is associated with a sync queue, but is_sync happens =
to be false;
>> - or the bic is associate with an async queue, but is_sync happens to =
be true.
>>=20
>> Of course, with these patches, the associations move from "with a
>> sync/async queue" to "with a set of sync/async queues, one per
>> actuator".
>=20
> My bad... The bic->bfqq[][actuator_idx] is an array of pointers... I =
was reading
> it as "&bic->bfqq[1][actuator_idx]". So please ignore. Apologies for =
the noise.
>=20

Great, then the last bit of action for me is to turn the offending
conditional operation into an if statement.  I'm going to do that and
send a V12 with this change, and with only this first patch still
needing your approval.

Thanks,
Paolo