linux-kernel - Re: [PATCH 3/6] lib/bucket_locks: use kvmalloc

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Message-ID: <CA+55aFyu9HpoHcn0p6uaADOspTd2DKPYciAgHz+C6zwLBvVSJA@mail.gmail.com>
Date:   Thu, 31 May 2018 10:01:51 -0500
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Davidlohr Bueso <dave@...olabs.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Graf <tgraf@...g.ch>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Manfred Spraul <manfred@...orfullife.com>,
        guillaume.knispel@...ersonicimagine.com,
        Linux API <linux-api@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 3/6] lib/bucket_locks: use kvmalloc_array()

On Wed, May 30, 2018 at 2:42 AM Michal Hocko <mhocko@...nel.org> wrote:
>
> That being sad, if you believe that silently fixing up a code like that
> is a good idea we can do the following of course:

Ack.

Except for:

> Linus argues that this just motivates people to do even
> more hacks like
>         if (gfp == GFP_KERNEL)
>                 kvmalloc
>         else
>                 kmalloc
>
> I haven't seen this happening but it is true that we can grow those in
> future.

This whole discussion came from the fact that YES, THIS IS ACTUALLY HAPPENING.

See lib/bucket_locks.c - it just uses gfpflags_allow_blocking()
instead of explicitly checking for GFP_KERNEL (probably because the
only two cases it actually deals with is GFP_ATOMIC and GFP_KERNEL).

              Linus