On Tue, Nov 16, 2021 at 1:27 PM Mina Almasry [off-list ref] wrote:

On Tue, Nov 16, 2021 at 3:29 AM Michal Hocko [off-list ref] wrote:

[...]

quoted

Yes, exactly. I meant that all this special casing would be done at the
shmem layer as it knows how to communicate this usecase.

Awesome. The more I think of it I think the ENOSPC handling is perfect
for this use case, because it gives all users of the shared memory and
remote chargers a chance to gracefully handle the ENOSPC or the SIGBUS
when we hit the nothing to kill case. The only issue is finding a
clean implementation, and if the implementation I just proposed sounds
good to you then I see no issues and I'm happy to submit this in the
next version. Shakeel and others I would love to know what you think
either now or when I post the next version.

The direction seems reasonable to me. I would have more comments on
the actual code. At the high level I would prefer not to expose these
cases in the filesystem code (shmem or others) and instead be done in
a new memcg interface for filesystem users.