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[209.85.208.171]) by smtp.gmail.com with ESMTPSA id g12sm15046644lfb.66.2020.04.08.09.20.17 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Apr 2020 09:20:17 -0700 (PDT) Received: by mail-lj1-f171.google.com with SMTP id r7so8222854ljg.13 for ; Wed, 08 Apr 2020 09:20:17 -0700 (PDT) X-Received: by 2002:a2e:9b8e:: with SMTP id z14mr5516543lji.150.1586362816627; Wed, 08 Apr 2020 09:20:16 -0700 (PDT) MIME-Version: 1.0 References: <20200408155924.107722-1-peterx@redhat.com> In-Reply-To: <20200408155924.107722-1-peterx@redhat.com> From: Linus Torvalds Date: Wed, 8 Apr 2020 09:20:00 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] mm/gup: Let __get_user_pages_locked() return -EINTR for fatal signal To: Peter Xu Cc: Linux-MM , Linux Kernel Mailing List , Andrew Morton , Hillf Danton , Thomas Gleixner , Peter Zijlstra , syzbot+3be1a33f04dc782e9fd5@syzkaller.appspotmail.com, Michal Hocko Content-Type: text/plain; charset="UTF-8" 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 Wed, Apr 8, 2020 at 8:59 AM Peter Xu wrote: > > __get_user_pages_locked() will return 0 instead of -EINTR after commit > 4426e945df588 which added extra code to allow gup detect fatal signal > faster. Restore that behavior. I've applied this, but it's worth noting that __get_user_pages_locked() can still return 0 in other situations. I realize that "I got zero pages" is a valid return value, but I do wonder if we should make the rule be that a zero return value isn't possible (return -EAGAIN or whatever if you doin't have the EFAULT/EINTR conditions). So that you'd always get either an error, or a successful number of pages. The only case where __get_user_pages_locked() might return zero is if you pass in a zero 'nr_pages', although I suspect even for that case returning -EINVAL might be a better option. Anyway, this is not a new issue, but I thought I'd mention it. Linus