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[209.85.208.42]) by smtp.gmail.com with ESMTPSA id va16-20020a17090711d000b0099bc0daf3d7sm9470585ejb.182.2023.08.02.10.49.52 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Aug 2023 10:49:52 -0700 (PDT) Received: by mail-ed1-f42.google.com with SMTP id 4fb4d7f45d1cf-522462d8416so11066a12.1 for ; Wed, 02 Aug 2023 10:49:52 -0700 (PDT) X-Received: by 2002:aa7:c0d2:0:b0:522:d6f4:c0eb with SMTP id j18-20020aa7c0d2000000b00522d6f4c0ebmr5009048edp.40.1690998591858; Wed, 02 Aug 2023 10:49:51 -0700 (PDT) MIME-Version: 1.0 References: <20230801220733.1987762-1-surenb@google.com> <20230801220733.1987762-5-surenb@google.com> In-Reply-To: <20230801220733.1987762-5-surenb@google.com> From: Linus Torvalds Date: Wed, 2 Aug 2023 10:49:35 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 4/6] mm: lock vma explicitly before doing vm_flags_reset and vm_flags_reset_once To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, jannh@google.com, willy@infradead.org, liam.howlett@oracle.com, david@redhat.com, peterx@redhat.com, ldufour@linux.ibm.com, vbabka@suse.cz, michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, hannes@cmpxchg.org, dave@stgolabs.net, hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 6CE89160018 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: usfp31kr5jfe9ofieb1p8wr13eu6xfmz X-HE-Tag: 1690998594-891691 X-HE-Meta: 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 TniYLdjX 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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 Tue, 1 Aug 2023 at 15:07, Suren Baghdasaryan wrote: > > To make locking more visible, change these > functions to assert that the vma write lock is taken and explicitly lock > the vma beforehand. So I obviously think this is a good change, but the fact that it touched driver files makes me go "we're still doing something wrong". I'm not super-happy with hfi1_file_mmap() doing something like vma_start_write(), in that I *really* don't think drivers should ever have to think about issues like this. And I think it's unnecessary. This is the mmap op in the hfi1_file_ops, and I think that any actual mmap() code had _better_ had locked the new vma before asking any driver to set things up (and the assert would catch it if somebody didn't). I realize that it doesn't hurt in a technical sense, but I think having drivers call these VM-internal subtle locking functions does hurt in a maintenance sense, so we should make sure to not have it. Linus