Re: [PATCH 0/1] Fix zero copy I/O on __get_user_pages allocated pages

[Pantelis Antoniou]

On Wed, 7 May 2025 14:50:18 -0700
Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Wed, 7 May 2025 10: 41: 04 -0500 Pantelis Antoniou <p. antoniou@
> partner. samsung. com> wrote: > Updates to network filesystems
> enabled zero copy I/O by using the > netfslib common accessors.
> Updates by whom? Are all the people who 
> On Wed, 7 May 2025 10:41:04 -0500 Pantelis Antoniou
> <p.antoniou@xxxxxxxxxxxxxxxxxxx> wrote:
> 
> > Updates to network filesystems enabled zero copy I/O by using the
> > netfslib common accessors.
> 
> Updates by whom?  Are all the people who need to know about this being
> cc'ed here?
> 

I think the first cover letter contains that information.

> > One example of that is the 9p filesystem which is commonly used in
> > qemu based setups for sharing files with the host.
> > 
> > In our emulation environment we have noticed failing writes when
> > performing I/O from a userspace mapped DRM GEM buffer object.
> > The platform does not use VRAM, all graphics memory is regular DRAM
> > memory, allocated via __get_free_pages
> 
> We should identify which kernel version(s) should be patched, please. 
> 6.16-rc1?  6.15?  -stable?
> 

The first occurance of the bug was on internal kernel tree that was
based on 6.8.

This patch is against 6.15-rc5.

> I often make these decisions but in this case I have far too little
> information to be able to do that.
> 

No worries.

I see that this is picked up for mm unstable as is? Do you want
me to generate a single patch merging the info of the cover letter
and the single patch?

The reason for the split is that I was not sure if you needed to
have all the sordid details included in the applied patch.

FWIW, we also have a buildroot patch that exhibits the problem
in a much simplified way that what the original bug report came about.
I don't think its appropriate content for the list, but I can
share if anyone is curious about it.

> Thanks.

Regards

-- Pantelis