Re: [PATCH V2] block: make segment size limit workable for > 4K PAGE_SIZE

[Ming Lei <ming.lei@redhat.com>]

On Thu, Feb 13, 2025 at 03:18:43PM +0100, Daniel Gomez wrote:
> On Thu, Feb 13, 2025 at 04:51:55PM +0100, Ming Lei wrote:
> > On Thu, Feb 13, 2025 at 12:30:29AM -0800, Christoph Hellwig wrote:
> > > On Thu, Feb 13, 2025 at 04:02:46PM +0800, Ming Lei wrote:
> > > > The problem[1] is that this kind of mmc card fails to be recognized as
> > > > block disk. Block layer io split code can handle this case actually.
> > > 
> > > When we still had bio_add_pc_page it would break the assumption that
> > > you could always add a full page.  With that gone and everything going
> > > through the split machinery we might be fine now, but backporting it
> > > to 6.13 and earlier will cause breakage.
> >  
> > Yes, I will mention the following two are depended for backporting in
> > commit log:
> > 
> > 02ee5d69e3ba block: remove blk_rq_bio_prep
> > 6aeb4f836480 block: remove bio_add_pc_page
> 
> Ming, is that sufficient for your use case? Or do you still need to remove the
> assumption that the "minimum" segment size is not PAGE_SIZE?

If you want to make any block device with < 64K max_segment_size working
on 64K page_size kernel, you need this patch and the following three
dependencies:

commit 6aeb4f836480 ("block: remove bio_add_pc_page")
commit 02ee5d69e3ba ("block: remove blk_rq_bio_prep")
commit b7175e24d6ac ("block: add a dma mapping iterator")


Thanks,
Ming