linux-kernel - Re: [PATCH] mm, oom: distinguish blockable mode for mmu notifiers

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Message-ID: <20180824164003.GW29735@dhcp22.suse.cz>
Date:   Fri, 24 Aug 2018 18:40:03 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Jerome Glisse <jglisse@...hat.com>
Cc:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Alex Deucher <alexander.deucher@....com>,
        David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        Dennis Dalessandro <dennis.dalessandro@...el.com>,
        Sudeep Dutt <sudeep.dutt@...el.com>,
        Ashutosh Dixit <ashutosh.dixit@...el.com>,
        Dimitri Sivanich <sivanich@....com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Felix Kuehling <felix.kuehling@....com>, kvm@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        xen-devel@...ts.xenproject.org,
        Christian König <christian.koenig@....com>,
        David Rientjes <rientjes@...gle.com>,
        Leon Romanovsky <leonro@...lanox.com>
Subject: Re: [PATCH] mm, oom: distinguish blockable mode for mmu notifiers

On Fri 24-08-18 11:12:40, Jerome Glisse wrote:
[...]
> I am fine with Michal patch, i already said so couple month ago first time
> this discussion did pop up, Michal you can add:
> 
> Reviewed-by: Jérôme Glisse <jglisse@...hat.com>

So I guess the below is the patch you were talking about?

>From f7ac75277d526dccd011f343818dc6af627af2af Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@...e.com>
Date: Fri, 24 Aug 2018 15:32:24 +0200
Subject: [PATCH] mm, mmu_notifier: be explicit about range invalition
 non-blocking mode

If invalidate_range_start is called for !blocking mode then all
callbacks have to guarantee they will no block/sleep. The same obviously
applies to invalidate_range_end because this operation pairs with the
former and they are called from the same context. Make sure this is
appropriately documented.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 include/linux/mmu_notifier.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 133ba78820ee..698e371aafe3 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -153,7 +153,9 @@ struct mmu_notifier_ops {
 	 *
 	 * If blockable argument is set to false then the callback cannot
 	 * sleep and has to return with -EAGAIN. 0 should be returned
-	 * otherwise.
+	 * otherwise. Please note that if invalidate_range_start approves
+	 * a non-blocking behavior then the same applies to
+	 * invalidate_range_end.
 	 *
 	 */
 	int (*invalidate_range_start)(struct mmu_notifier *mn,
-- 
2.18.0

-- 
Michal Hocko
SUSE Labs