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Date:   Thu, 5 Oct 2023 15:32:29 +0200
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Subject: Re: [PATCH 21/21] nvme: Support atomic writes
To:     John Garry <john.g.garry@oracle.com>,
        Alan Adamson <alan.adamson@oracle.com>
CC:     <axboe@kernel.dk>, <kbusch@kernel.org>, <hch@lst.de>,
        <sagi@grimberg.me>, <jejb@linux.ibm.com>,
        <martin.petersen@oracle.com>, <djwong@kernel.org>,
        <viro@zeniv.linux.org.uk>, <brauner@kernel.org>,
        <chandan.babu@oracle.com>, <dchinner@redhat.com>,
        <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-nvme@lists.infradead.org>, <linux-xfs@vger.kernel.org>,
        <linux-fsdevel@vger.kernel.org>, <tytso@mit.edu>,
        <jbongio@google.com>, <linux-api@vger.kernel.org>
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From:   Pankaj Raghav <p.raghav@samsung.com>
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References: <20230929102726.2985188-1-john.g.garry@oracle.com>
        <20230929102726.2985188-22-john.g.garry@oracle.com>
        <CGME20231004113943eucas1p23a51ce5ef06c36459f826101bb7b85fc@eucas1p2.samsung.com>
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        <b6ed0e26-e3d4-40c1-b95d-11c5b3b71077@oracle.com>
Precedence: bulk

>>> +                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);
>>> +            }
>>>
>