From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Michal Hocko <mhocko@suse.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: slab_pre_alloc_hook() strips __GFP_NOLOCKDEP away.
Date: Wed, 23 Mar 2022 12:30:08 +0100 [thread overview]
Message-ID: <YjsEwM/jQsAKbkYP@linutronix.de> (raw)
In-Reply-To: <5d0cd87a-564e-8b44-f81b-154f21776ccd@suse.cz>
On 2022-03-23 11:09:35 [+0100], Vlastimil Babka wrote:
> > --- a/mm/slab.h
> > +++ b/mm/slab.h
> > @@ -717,7 +717,7 @@ static inline struct kmem_cache *slab_pre_alloc_hook(struct kmem_cache *s,
> > struct obj_cgroup **objcgp,
> > size_t size, gfp_t flags)
> > {
> > - flags &= gfp_allowed_mask;
> > + flags &= gfp_allowed_mask | __GFP_NOLOCKDEP;
>
> Hmm but gfp_allowed_mask already should contain __GFP_NOLOCKDEP after
> kernel_init_freeable() is reached. I doubt we can reach fs or reclaim
> code before that?
That is way past init. I have
gfp_allowed_mask = 0x1ffffff
__GFP_NOLOCKDEP = 0x8000000
Looking at the origin of gfp_allowed_mask
| /* Room for N __GFP_FOO bits */
| #define __GFP_BITS_SHIFT (24 + \
| 3 * IS_ENABLED(CONFIG_KASAN_HW_TAGS) + \
| IS_ENABLED(CONFIG_LOCKDEP))
| #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
which in my case 24 + 1 but it would need to be something like
27 * IS_ENABLED(CONFIG_LOCKDEP)
or a better way to come up with __GFP_BITS_MASK.
Sebastian
next prev parent reply other threads:[~2022-03-23 11:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-22 17:39 slab_pre_alloc_hook() strips __GFP_NOLOCKDEP away Sebastian Andrzej Siewior
2022-03-23 10:09 ` Vlastimil Babka
2022-03-23 11:30 ` Sebastian Andrzej Siewior [this message]
2022-03-23 11:45 ` Vlastimil Babka
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