Re: [PATCH RFC 2/7] md/raid0: convert raid0_handle_discard() to use bio_submit_split()

[Christoph Hellwig <hch@infradead.org>]

On Tue, Aug 26, 2025 at 09:08:33AM +0800, Yu Kuai wrote:
> 在 2025/08/25 18:57, Christoph Hellwig 写道:
> > On Mon, Aug 25, 2025 at 05:36:55PM +0800, Yu Kuai wrote:
> > > +		bio = bio_submit_split(bio,
> > > +				zone->zone_end - bio->bi_iter.bi_sector,
> > > +				&mddev->bio_set);
> > 
> > Do you know why raid0 and linear use mddev->bio_set for splitting
> > instead of their own split bio_sets like raid1/10/5?  Is this safe?
> > 
> 
> I think it's not safe, as mddev->bio_split pool size is just 2, reuse
> this pool to split multiple times before submitting will need greate
> pool size to make this work.
> 
> By the way, do you think it's better to increate disk->bio_split pool
> size to 4 and convert all mdraid internal split to use disk->bio_split
> directly?

I don't really know where that magic number 4 or even the current number
comes from, but I think Jens might be amenable to a small increase with a
good explanation.