Re: [PATCH 21/21] nvme: Support atomic writes

From: John Garry
Date: Thu Oct 05 2023 - 12:22:41 EST


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