Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL

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To: Barry Song <21cnbao@xxxxxxxxx>
Subject: Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
From: Michal Hocko <mhocko@xxxxxxxx>
Date: Fri, 19 Jul 2024 09:02:01 +0200
Cc: akpm@xxxxxxxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, Barry Song <v-songbaohua@xxxxxxxx>, Uladzislau Rezki <urezki@xxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, Lorenzo Stoakes <lstoakes@xxxxxxxxx>, Christoph Lameter <cl@xxxxxxxxx>, Pekka Enberg <penberg@xxxxxxxxxx>, David Rientjes <rientjes@xxxxxxxxxx>, Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>, Vlastimil Babka <vbabka@xxxxxxx>, Roman Gushchin <roman.gushchin@xxxxxxxxx>, Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
In-reply-to: <CAGsJ_4wNre89_pQWvU0jj6reLaETYOTUVu3DYwPo8Up1DM1-8A@mail.gmail.com>
References: <Zpi9JJGUih2_VAMF@tiehlicka> <CAGsJ_4x0Bak+H0zJNH4FKLqd-Dmm4HhT5S4CzsoUaNiDKHNTtA@mail.gmail.com> <ZpjD7PKBOOzZU0sp@tiehlicka> <CAGsJ_4w0dJyJhYLe4T908=fGUC54yHcNaCA22QBN8OSkpxTrqg@mail.gmail.com> <ZpjJpvu5xWlDx4gD@tiehlicka> <CAGsJ_4wzpSLbteULhnTrQa_p5ETjiCTRHfF9Ph34=WZiub3irA@mail.gmail.com> <ZpjTMc3wLuzFX6OD@tiehlicka> <CAGsJ_4wRa6YWY=7dMhv2BAX5Mdh0b9uy3=S9W6nd_-1yANb8Zg@mail.gmail.com> <ZpjXacbUGxTs9cR0@tiehlicka> <CAGsJ_4wNre89_pQWvU0jj6reLaETYOTUVu3DYwPo8Up1DM1-8A@mail.gmail.com>

On Fri 19-07-24 12:35:55, Barry Song wrote:
> On Thu, Jul 18, 2024 at 8:50 PM Michal Hocko <mhocko@xxxxxxxx> wrote:
[...]
> > Yes, those shouldn't really fail. NOWAIT|NOFAIL was something that
> > should never happen and I really hope it doesn't. Others should really
> > retry but it's been some time since I've checked the last time.
> 
> 
> I assume allocations directly using alloc_pages() might not respect GFP_NOFAIL
> and violate the semantics of GFP_NOFAIL.

What do you mean?
 
> Additionally, at least drivers/vdpa/vdpa_user/iova_domain.c is
> incorrect with GFP_ATOMIC
> | __GFP_NOFAIL.

This is broken! Please bring this up with the maintainer of the code.

[...]

> GFP_NOFAIL things need to be fixed. Let me investigate further.

Thanks!

-- 
Michal Hocko
SUSE Labs

Follow-Ups:
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Christoph Hellwig
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Barry Song

References:
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Michal Hocko
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Barry Song
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Michal Hocko
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Barry Song
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Michal Hocko
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Barry Song
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Michal Hocko
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Barry Song
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Michal Hocko
- Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL
  - From: Barry Song

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