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bh=EIPupChmZWdqCbipzzk6WIge6ktn1mIlacRGTtLMASA=; b=plb39T261+q73vUMZloi+nvkH8nnyo+NMJ3mWpZsLfYYmeWt/WorRYCmo/s5C1ChCTGt2v 3zeJW7/3Quy+a++wy39qc2ym1EPIKxsP++jtuZtDVsjGQBIcgFFF7gE5Hjqq1lrrCau9wl eZlhFhYILXyWtEI3TjhVbj0vmXaTico= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 2C2211348C; Wed, 1 Feb 2023 07:43:44 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id UybHCTAY2mOWMwAAMHmgww (envelope-from ); Wed, 01 Feb 2023 07:43:44 +0000 Date: Wed, 1 Feb 2023 08:43:43 +0100 From: Michal Hocko To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@techsingularity.net, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org, mingo@redhat.com, will@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, rppt@kernel.org, 42.hyeyoo@gmail.com, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, leewalsh@google.com, posk@google.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 1/1] mm: introduce vm_flags_reset_once to replace WRITE_ONCE vm_flags updates Message-ID: References: <20230201000116.1333160-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230201000116.1333160-1-surenb@google.com> X-Stat-Signature: mxmcjmrxi4z7ifytarx7c318jmqq1wu3 X-Rspam-User: X-Rspamd-Queue-Id: E9D6D40009 X-Rspamd-Server: rspam06 X-HE-Tag: 1675237425-416157 X-HE-Meta: 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 V+GsmeTB tHDjaiT+zwREQzhwiRgxLVZsY9YZ5Y3fSXH9ieg3BqV4lqbmBEbnnk7ebqDbLAeCfMQepxC0oPQl1VuHlzy56O9jl0bsOWXQ6i9a2kwluG3Zm7HgPO199gfecESrGJUmwbDGWN3tc2XkzMgnQBY3NLblRTzuDPGh+FdGqbJwVRRW0vRbp+QlgW2gIH7yLtHIxCU0JJ6JlME2rKQNgnHfzH7YmIAqnPQAcWPDujLmloz8fnqB0SxFVH4iJgH4a18GqfYFzgdh4wSHqra6pXM67b/gtNFws815boI6PXYmAZBNGPZXHZla6cggT558xI+OnOym2PMPhxdrFX0Go9LtPvmWcpUJrIcRAuFHItWaJ+MVirDD6ADPF4CfSRuLUd2Ao1e8b5b5MVBNv6V0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 31-01-23 16:01:16, Suren Baghdasaryan wrote: > Provide vm_flags_reset_once() and replace the vm_flags updates which used > WRITE_ONCE() to prevent compiler optimizations. > > Fixes: 0cce31a0aa0e ("mm: replace vma->vm_flags direct modifications with modifier calls") > Reported-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> > Signed-off-by: Suren Baghdasaryan This would have been better folded into the vm_flags modification patch because it would be more obvious change. Hugh has provided a very nice comment in mlock_vma_pages_range but the git blame would be more visible when the conversion is from WRITE_ONCE. One way or the other Acked-by: Michal Hocko > --- > Notes: > - The patch applies cleanly over mm-unstable > - The SHA in Fixes: line is from mm-unstable, so is... unstable > > include/linux/mm.h | 7 +++++++ > mm/mlock.c | 4 ++-- > 2 files changed, 9 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 5bf0ad48faaa..23ce04f6e91e 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -648,6 +648,13 @@ static inline void vm_flags_reset(struct vm_area_struct *vma, > vm_flags_init(vma, flags); > } > > +static inline void vm_flags_reset_once(struct vm_area_struct *vma, > + vm_flags_t flags) > +{ > + mmap_assert_write_locked(vma->vm_mm); > + WRITE_ONCE(ACCESS_PRIVATE(vma, __vm_flags), flags); > +} > + > static inline void vm_flags_set(struct vm_area_struct *vma, > vm_flags_t flags) > { > diff --git a/mm/mlock.c b/mm/mlock.c > index ed49459e343e..617469fce96d 100644 > --- a/mm/mlock.c > +++ b/mm/mlock.c > @@ -380,7 +380,7 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma, > */ > if (newflags & VM_LOCKED) > newflags |= VM_IO; > - vm_flags_reset(vma, newflags); > + vm_flags_reset_once(vma, newflags); > > lru_add_drain(); > walk_page_range(vma->vm_mm, start, end, &mlock_walk_ops, NULL); > @@ -388,7 +388,7 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma, > > if (newflags & VM_IO) { > newflags &= ~VM_IO; > - vm_flags_reset(vma, newflags); > + vm_flags_reset_once(vma, newflags); > } > } > > -- > 2.39.1.456.gfc5497dd1b-goog -- Michal Hocko SUSE Labs