[PATCH 1/2] block: accumulate segment page gaps per bio

[Christoph Hellwig]

On Mon, Aug 11, 2025 at 09:27:18AM -0600, Keith Busch wrote:
> I initially tried to copy the nsegs usage in the request, but there are
> multiple places (iomap, xfs, and btrfs) that split to hardware limits
> without a request, so I'm not sure where the result is supposed to go to
> be referenced later. Or do those all call the same split function later
> in the generic block layer, in which case it shouldn't matter if the
> upper layers already called it?

Yes, we'll always end up calling into __bio_split_to_limits in blk-mq,
no matter if someone split before.  The upper layer splits are only
for zone append users that can't later be split, but
__bio_split_to_limits is stilled called on them to count the segments
and to assert that they don't need splitting.