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[99.254.144.39]) by smtp.gmail.com with ESMTPSA id t18-20020a0cea32000000b005ef54657ea0sm3221971qvp.126.2023.06.12.06.59.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jun 2023 06:59:22 -0700 (PDT) Date: Mon, 12 Jun 2023 09:59:19 -0400 From: Peter Xu To: Suren Baghdasaryan Cc: Matthew Wilcox , 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, ying.huang@intel.com, david@redhat.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v2 2/6] mm: handle swap page faults under VMA lock if page is uncontended Message-ID: References: <20230609005158.2421285-1-surenb@google.com> <20230609005158.2421285-3-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 09, 2023 at 03:34:34PM -0700, Suren Baghdasaryan wrote: > On Fri, Jun 9, 2023 at 1:45 PM Peter Xu wrote: > > > > On Fri, Jun 09, 2023 at 09:35:49PM +0100, Matthew Wilcox wrote: > > > On Fri, Jun 09, 2023 at 04:25:42PM -0400, Peter Xu wrote: > > > > > bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm, > > > > > unsigned int flags) > > > > > { > > > > > + /* Can't do this if not holding mmap_lock */ > > > > > + if (flags & FAULT_FLAG_VMA_LOCK) > > > > > + return false; > > > > > > > > If here what we need is the page lock, can we just conditionally release > > > > either mmap lock or vma lock depending on FAULT_FLAG_VMA_LOCK? > > > > > > See patch 5 ... > > > > Just reaching.. :) > > > > Why not in one shot, then? > > I like small incremental changes, but I can squash them if that helps > in having a complete picture. Yes that'll be appreciated. IMHO keeping changing semantics of FAULT_FLAG_VMA_LOCK for the folio lock function in the same small series is confusing. -- Peter Xu