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Thu, 13 Jul 2023 20:03:27 -0700 (PDT) MIME-Version: 1.0 References: <20230711202047.3818697-1-willy@infradead.org> <20230711202047.3818697-3-willy@infradead.org> In-Reply-To: <20230711202047.3818697-3-willy@infradead.org> From: Suren Baghdasaryan Date: Thu, 13 Jul 2023 20:03:16 -0700 Message-ID: Subject: Re: [PATCH v2 2/9] mm: Allow per-VMA locks on file-backed VMAs To: "Matthew Wilcox (Oracle)" Cc: linux-mm@kvack.org, Arjun Roy , Eric Dumazet , linux-fsdevel@vger.kernel.org, Punit Agrawal Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: BA0F5C0007 X-Stat-Signature: 9jyia9kni5drux6ep7n6snc68wmh4cdi X-Rspam-User: X-HE-Tag: 1689303808-736659 X-HE-Meta: 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 2p3YgB6I fl6EVE7UgNKoQWZ5yTV3bQQB0FXKWot3RcFsuYxHZgjSUZC/oUg8cWMHrG+/jJkKNZlBcXKZMAi7pvgQIx8zOiISVTDMsMF50ooyt4IwelfU3zTmahz0eLM5fBClS2WiWMu/esWSRjOUqIz4CWhDmtPZgp9JTDUEWkbWZKiq7tuI4rQSesojueTgVTlvobmFjRJP4iwuRjcgvDrgzmAoLVOWOGW9Mp5RqSNpQ8rNb0ZNPqb7Q5S2XVLNH0DyQ0I8Kc2UfY03ZooHWMaXzRyiniYvFZ2gUNjixdvune7KFdujP/6dLe1pcKpTd7Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000008, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jul 11, 2023 at 1:21=E2=80=AFPM Matthew Wilcox (Oracle) wrote: > > The fault path will immediately fail in handle_mm_fault(), so this > is the minimal step which allows the per-VMA lock to be taken on > file-backed VMAs. There may be a small performance reduction as a > little unnecessary work will be done on each page fault. See later > patches for the improvement. > > Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Suren Baghdasaryan > --- > mm/memory.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 2c7967632866..f2dcc695f54e 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5247,6 +5247,11 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *= vma, unsigned long address, > goto out; > } > > + if ((flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vma)) { > + vma_end_read(vma); > + return VM_FAULT_RETRY; > + } > + > /* > * Enable the memcg OOM handling for faults triggered in user > * space. Kernel faults are handled more gracefully. > @@ -5418,12 +5423,8 @@ struct vm_area_struct *lock_vma_under_rcu(struct m= m_struct *mm, > if (!vma) > goto inval; > > - /* Only anonymous vmas are supported for now */ > - if (!vma_is_anonymous(vma)) > - goto inval; > - > /* find_mergeable_anon_vma uses adjacent vmas which are not locke= d */ > - if (!vma->anon_vma) > + if (vma_is_anonymous(vma) && !vma->anon_vma) > goto inval; > > if (!vma_start_read(vma)) > -- > 2.39.2 >