Re: [PATCH 1/2] bcachefs: do not use PF_MEMALLOC_NORECLAIM

Kent Overstreet
2024-08-26T19:43:08Z

On Mon, Aug 26, 2024 at 08:41:42PM GMT, Matthew Wilcox wrote:
> On Mon, Aug 26, 2024 at 03:39:47PM -0400, Kent Overstreet wrote:
> > Given the amount of plumbing required here, it's clear that passing gfp
> > flags is the less safe way of doing it, and this really does belong in
> > the allocation context.
> >
> > Failure to pass gfp flags correctly (which we know is something that
> > happens today, e.g. vmalloc -> pte allocation) means you're introducing
> > a deadlock.
>
> The problem with vmalloc is that the page table allocation _doesn't_
> take a GFP parameter.

yeah, I know. I posted patches to plumb it through, which were nacked by
Linus.

And we're trying to get away from passing gfp flags directly, are we
not? I just don't buy the GFP_NOFAIL unsafety argument.