linux-kernel - Re: [PATCH 21/21] nvme: Support atomic writes

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Message-ID: <83f58662-d737-44b0-9899-c0519a75968a@samsung.com>
Date:   Thu, 5 Oct 2023 15:32:29 +0200
From:   Pankaj Raghav <p.raghav@...sung.com>
To:     John Garry <john.g.garry@...cle.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

>>> +                blk_queue_atomic_write_max_bytes(disk->queue, atomic_bs);
>>> +                blk_queue_atomic_write_unit_min_sectors(disk->queue, 1);
>>> +                blk_queue_atomic_write_unit_max_sectors(disk->queue,
>>> +                                    atomic_bs / bs);
>> blk_queue_atomic_write_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 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);


> Thanks,
> John
> 
>>> +                blk_queue_atomic_write_boundary_bytes(disk->queue, boundary);
>>> +            } else {
>>> +                dev_err(ns->ctrl->device, "Unsupported atomic boundary=0x%x\n",
>>> +                    boundary);
>>> +            }
>>>
>