Re: [PATCH] mm/vmalloc: fix mischeck pfn valid in vmap_pfns

[Huan Yang]

HI Hillf,

Thanks fo your suggestion.

在 2025/3/19 19:26, Hillf Danton 写道:
> On Wed, 19 Mar 2025 09:08:51 +0100 Christoph Hellwig wrote:
> > On Wed, Mar 19, 2025 at 01:03:55PM +0800, Hillf Danton wrote:
> > > A quick fix is to add a vmap_pfn variant to walk around the pfn
> > > check in question, like the following diff (just for idea show).
> > No.
> Patient to see your fix, given no low hanging peach left for Mr Folio
> in case of HVO, (feel free to ignore, who is likely about 2.6-mile
> less tough than you could be).

I now believe there are two way to resolve the HVO folio can't vmap in udmabuf.

1. simple copy vmap_pfn code, don't bother common vmap_pfn, use by itself and remove pfn_valid check.

2. implement folio array based vmap(vmap_folios), which can given a range of each folio(offset, nr_pages), so can suit HVO folio's vmap.

1 is simple and can fast fix this issue, but may not too good. I need discuss with bot Christoph and udmabuf's maintainer.

2 is hard, but may worth to research, which I also will try to do. :)