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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1ptgb2-007wdp-Md; Tue, 02 May 2023 03:22:32 +0000 Date: Tue, 2 May 2023 04:22:32 +0100 From: Matthew Wilcox To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH 1/3] mm: handle swap page faults under VMA lock if page is uncontended Message-ID: References: <20230501175025.36233-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: A5C6E80A8B X-Stat-Signature: injkhbn9x1q6bx49tai81hidp7f4j4tj X-Rspam-User: X-HE-Tag: 1683001742-345904 X-HE-Meta: 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 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 Mon, May 01, 2023 at 07:30:13PM -0700, Suren Baghdasaryan wrote: > On Mon, May 1, 2023 at 7:02 PM Matthew Wilcox wrote: > > > > On Mon, May 01, 2023 at 10:50:23AM -0700, Suren Baghdasaryan wrote: > > > +++ b/mm/memory.c > > > @@ -3711,11 +3711,6 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > > > if (!pte_unmap_same(vmf)) > > > goto out; > > > > > > - if (vmf->flags & FAULT_FLAG_VMA_LOCK) { > > > - ret = VM_FAULT_RETRY; > > > - goto out; > > > - } > > > - > > > entry = pte_to_swp_entry(vmf->orig_pte); > > > if (unlikely(non_swap_entry(entry))) { > > > if (is_migration_entry(entry)) { > > > > You're missing the necessary fallback in the (!folio) case. > > swap_readpage() is synchronous and will sleep. > > True, but is it unsafe to do that under VMA lock and has to be done > under mmap_lock? ... you were the one arguing that we didn't want to wait for I/O with the VMA lock held?