Re: [PATCH 2/2] mm: drop PF_MEMALLOC_NORECLAIM

Michal Hocko
2024-08-26T16:51:57Z

On Mon 26-08-24 14:59:29, Matthew Wilcox wrote:
> On Mon, Aug 26, 2024 at 10:47:13AM +0200, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@suse.com>
> >
> > There is no existing user of the flag and the flag is dangerous because
> > a nested allocation context can use GFP_NOFAIL which could cause
> > unexpected failure. Such a code would be hard to maintain because it
> > could be deeper in the call chain.
> >
> > PF_MEMALLOC_NORECLAIM has been added even when it was pointed out [1]
> > that such a allocation contex is inherently unsafe if the context
> > doesn't fully control all allocations called from this context.
>
> Wouldn't a straight-up revert of eab0af905bfc be cleaner? Or is there
> a reason to keep PF_MEMALLOC_NOWARN?

I wanted to make it PF_MEMALLOC_NORECLAIM specific. I do not have a
strong case against PF_MEMALLOC_NOWARN TBH. It is a hack because the
scope is claiming something about all allocations within the scope
without necessarily knowing all of them (including potential future
changes). But NOWARN is not really harmful so I do not care strongly.

If a plan revert is preferably, I will go with it.
--
Michal Hocko
SUSE Labs