Re: [PATCH v2 5/5] block: use chunk_sectors when evaluating stacked atomic write limits

[Nilay Shroff]

On 6/18/25 2:07 PM, John Garry wrote:
> The atomic write unit max value is limited by any stacked device stripe
> size.
> 
> It is required that the atomic write unit is a power-of-2 factor of the
> stripe size.
> 
> Currently we use io_min limit to hold the stripe size, and check for a
> io_min <= SECTOR_SIZE when deciding if we have a striped stacked device.
> 
> Nilay reports that this causes a problem when the physical block size is
> greater than SECTOR_SIZE [0].
> 
> Furthermore, io_min may be mutated when stacking devices, and this makes
> it a poor candidate to hold the stripe size. Such an example (of when
> io_min may change) would be when the io_min is less than the physical
> block size.
> 
> Use chunk_sectors to hold the stripe size, which is more appropriate.
> 
> [0] https://lore.kernel.org/linux-block/888f3b1d-7817-4007-b3b3-1a2ea04df771@xxxxxxxxxxxxx/T/#mecca17129f72811137d3c2f1e477634e77f06781
> 
> Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>

Looks good to me:
Reviewed-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>