Re: [PATCH v5 07/12] md: support to align bio to limits

Hi,

在 2026/1/16 23:08, Christoph Hellwig 写道:
> On Thu, Jan 15, 2026 at 01:12:35AM +0800, Yu Kuai wrote:
>> For personalities that report optimal IO size, it indicates that users
>> can get the best IO bandwidth if they issue IO with this size. However
>> there is also an implicit condition that IO should also be aligned to the
>> optimal IO size.
>>
>> Currently, bio will only be split by limits, if bio offset is not aligned
>> to limits, then all split bio will not be aligned. This patch add a new
>> feature to align bio to limits first, and following patches will support
>> this for each personality if necessary.
> This feels a bit odd and mixes up different things as right now
> nothing in the block layer splits to the opt_io size.  If you want
> a boundary that is split on, the chunk_size limit seems to be what
> you want, and the existing code would do the work based on that.

No, the chunk_sectors and io_opt are different, and align io to io_opt
is not a general idea, for now this is the only requirement in mdraid.

Not sure if you remembered, Coly used to send a version to align IO to
io_opt separately, and we discussed and both agree align max_sectors to
io_opt and then align io to max_sectors in mdraid is better.

For now, current setting of max_sectors, and split IO to max_sectors
does not make much sense for raid0/10/456.

>
-- 
Thansk,
Kuai