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Message-ID: <008b8ad7-d6c0-e026-9e12-1a4d92848c4c@oracle.com>
Date: Thu, 5 Oct 2023 16:05:50 +0100
From: John Garry <john.g.garry@...cle.com>
To: Pankaj Raghav <p.raghav@...sung.com>,
Alan Adamson <alan.adamson@...cle.com>
Cc: 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,
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 21/21] nvme: Support atomic writes
On 05/10/2023 14:32, Pankaj Raghav wrote:
>>> te_unit_[min| max]_sectors expects sectors (512 bytes unit)
>>> as input but no conversion is done here from device logical block size
>>> to SECTORs.
>> Yeah, you are right. I think that we can just use:
>>
>> blk_queue_atomic_write_unit_max_sectors(disk->queue,
>> atomic_bs >> SECTOR_SHIFT);
>>
> Makes sense.
> I still don't grok the difference between max_bytes and unit_max_sectors here.
> (Maybe NVMe spec does not differentiate it?)
I think that max_bytes does not need to be a power-of-2 and could be
relaxed.
Having said that, max_bytes comes into play for merging of bios - so if
we are in a scenario with no merging, then may a well leave
atomic_write_max_bytes == atomic_write_unit_max.
But let us check this proposal to relax.
>
> I assume min_sectors should be as follows instead of setting it to 1 (512 bytes)?
>
> blk_queue_atomic_write_unit_min_sectors(disk->queue, bs >> SECTORS_SHIFT);
Yeah, right, we want unit_min to be the logical block size.
Thanks,
John
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