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Message-ID: <53bfe07e-e125-7a69-4f89-481c10e0959e@oracle.com>
Date: Mon, 2 Oct 2023 12:27:52 +0100
From: John Garry <john.g.garry@...cle.com>
To: Bart Van Assche <bvanassche@....org>, axboe@...nel.dk,
kbusch@...nel.org, hch@....de, sagi@...mberg.me,
jejb@...ux.ibm.com, martin.petersen@...cle.com, djwong@...nel.org,
viro@...iv.linux.org.uk, brauner@...nel.org,
chandan.babu@...cle.com, dchinner@...hat.com
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-nvme@...ts.infradead.org, linux-xfs@...r.kernel.org,
linux-fsdevel@...r.kernel.org, tytso@....edu, jbongio@...gle.com,
linux-api@...r.kernel.org
Subject: Re: [PATCH 18/21] scsi: sd: Support reading atomic properties from
block limits VPD
On 29/09/2023 18:54, Bart Van Assche wrote:
> On 9/29/23 03:27, John Garry wrote:
>> +static void sd_config_atomic(struct scsi_disk *sdkp)
>> +{
>> + unsigned int logical_block_size = sdkp->device->sector_size;
>> + struct request_queue *q = sdkp->disk->queue;
>> +
>> + if (sdkp->max_atomic) {
>
> Please use the "return early" style here to keep the indentation
> level in this function low.
ok, fine.
>
>> + unsigned int max_atomic = max_t(unsigned int,
>> + rounddown_pow_of_two(sdkp->max_atomic),
>> + rounddown_pow_of_two(sdkp->max_atomic_with_boundary));
>> + unsigned int unit_min = sdkp->atomic_granularity ?
>> + rounddown_pow_of_two(sdkp->atomic_granularity) :
>> + physical_block_size_sectors;
>> + unsigned int unit_max = max_atomic;
>> +
>> + if (sdkp->max_atomic_boundary)
>> + unit_max = min_t(unsigned int, unit_max,
>> + rounddown_pow_of_two(sdkp->max_atomic_boundary));
>
> Why does "rounddown_pow_of_two()" occur in the above code?
I assume that you are talking about all the code above to calculate
atomic write values for the device.
The reason is that atomic write unit min and max are always a power-of-2
- see rules described earlier - as so that we why we rounddown to a
power-of-2.
Thanks,
John
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