From: Michal Hocko <mhocko@kernel.org>
To: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2] mm/kvmalloc: do not call kmalloc for size > KMALLOC_MAX_SIZE
Date: Mon, 5 Nov 2018 17:57:30 +0100 [thread overview]
Message-ID: <20181105165730.GN4361@dhcp22.suse.cz> (raw)
In-Reply-To: <d033db53-129d-c031-db78-ba7f9fed5bf4@yandex-team.ru>
On Mon 05-11-18 19:19:28, Konstantin Khlebnikov wrote:
>
>
> On 05.11.2018 16:03, Vlastimil Babka wrote:
> > On 11/1/18 11:09 AM, Konstantin Khlebnikov wrote:
> > > Allocations over KMALLOC_MAX_SIZE could be served only by vmalloc.
> > >
> > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> >
> > Makes sense regardless of warnings stuff.
> >
> > Acked-by: Vlastimil Babka <vbabka@suse.cz>
> >
> > But it must be moved below the GFP_KERNEL check!
>
> But kmalloc cannot handle it regardless of GFP.
>
> Ok maybe write something like this
>
> if (size > KMALLOC_MAX_SIZE) {
> if (WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL)
> return NULL;
> goto do_vmalloc;
> }
Do we really have to be so defensive? I agree with Vlastimil that the
check should be done after GFP_KERNEL check (I should have noticed that).
kmalloc should already complain on the allocation size request.
> or fix that uncertainty right in vmalloc
>
> For now comment in vmalloc declares
>
> * Any use of gfp flags outside of GFP_KERNEL should be consulted
> * with mm people.
Which is what we want. There are some exceptional cases where using a
subset of GFP_KERNEL works fine (e.g. scope nofs/noio context).
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2018-11-05 16:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-01 9:12 [PATCH] mm/kvmalloc: do not confuse kmalloc with page order over MAX_ORDER Konstantin Khlebnikov
2018-11-01 9:33 ` Michal Hocko
2018-11-01 10:09 ` [PATCH 2] mm/kvmalloc: do not call kmalloc for size > KMALLOC_MAX_SIZE Konstantin Khlebnikov
2018-11-01 10:24 ` Michal Hocko
2018-11-01 10:48 ` Konstantin Khlebnikov
2018-11-01 12:55 ` Michal Hocko
2018-11-01 16:42 ` Konstantin Khlebnikov
2018-11-01 16:55 ` Michal Hocko
2018-11-05 13:03 ` Vlastimil Babka
2018-11-05 16:19 ` Konstantin Khlebnikov
2018-11-05 16:52 ` Vlastimil Babka
2018-11-05 16:57 ` Michal Hocko [this message]
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