From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8C825C2F421 for ; Mon, 21 Jan 2019 15:58:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5D4E720823 for ; Mon, 21 Jan 2019 15:58:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729344AbfAUP6K (ORCPT ); Mon, 21 Jan 2019 10:58:10 -0500 Received: from mx2.suse.de ([195.135.220.15]:38230 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728761AbfAUP6K (ORCPT ); Mon, 21 Jan 2019 10:58:10 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 3BEE3AC3B; Mon, 21 Jan 2019 15:58:09 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 21 Jan 2019 16:58:07 +0100 From: Roman Penyaev To: Jens Axboe Cc: linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-block@vger.kernel.org, hch@lst.de, jmoyer@redhat.com, avi@scylladb.com, linux-block-owner@vger.kernel.org Subject: Re: [PATCH 05/17] Add io_uring IO interface In-Reply-To: <801e00ef-b21d-4420-9fa3-2b19fe2398b2@kernel.dk> References: <20190118161225.4545-1-axboe@kernel.dk> <20190118161225.4545-6-axboe@kernel.dk> <20204806b30147da55990e639586cce1@suse.de> <801e00ef-b21d-4420-9fa3-2b19fe2398b2@kernel.dk> Message-ID: X-Sender: rpenyaev@suse.de User-Agent: Roundcube Webmail Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2019-01-21 16:30, Jens Axboe wrote: > On 1/21/19 2:13 AM, Roman Penyaev wrote: >> On 2019-01-18 17:12, Jens Axboe wrote: >> >> [...] >> >>> + >>> +static int io_uring_create(unsigned entries, struct io_uring_params >>> *p, >>> + bool compat) >>> +{ >>> + struct user_struct *user = NULL; >>> + struct io_ring_ctx *ctx; >>> + int ret; >>> + >>> + if (entries > IORING_MAX_ENTRIES) >>> + return -EINVAL; >>> + >>> + /* >>> + * Use twice as many entries for the CQ ring. It's possible for the >>> + * application to drive a higher depth than the size of the SQ >>> ring, >>> + * since the sqes are only used at submission time. This allows for >>> + * some flexibility in overcommitting a bit. >>> + */ >>> + p->sq_entries = roundup_pow_of_two(entries); >>> + p->cq_entries = 2 * p->sq_entries; >>> + >>> + if (!capable(CAP_IPC_LOCK)) { >>> + user = get_uid(current_user()); >>> + ret = __io_account_mem(user, ring_pages(p->sq_entries, >>> + p->cq_entries)); >>> + if (ret) { >>> + free_uid(user); >>> + return ret; >>> + } >>> + } >>> + >>> + ctx = io_ring_ctx_alloc(p); >>> + if (!ctx) >>> + return -ENOMEM; >> >> Hi Jens, >> >> It seems pages should be "unaccounted" back here and uid freed if path >> with "if (!capable(CAP_IPC_LOCK))" above was taken. > > Thanks, yes that is leaky. I'll fix that up. > >> But really, could please someone explain me what is wrong with >> allocating >> all urings in mmap() without touching RLIMIT_MEMLOCK at all? Thus all >> memory will be accounted to the caller app and if app is greedy it >> will >> be killed by oom. What I'm missing? > > I don't really what that'd change, if we do it off the ->mmap() or when > we setup the io_uring instance with io_uring_setup(2). We need this > memory > to be pinned, we can't fault on it. Hm, I thought that for pinning there is a separate counter ->pinned_vm (introduced by bc3e53f682d9 ("mm: distinguish between mlocked and pinned pages") Which seems not wired up with anything, just a counter, used by couple of drivers. Hmmm.. Frankly, now I am lost. You map these pages through remap_pfn_range(), so virtual user mapping won't fault, right? And these pages you allocate with GFP_KERNEL, so they are already pinned. So now I do not understand why this accounting is needed at all :) The only reason I had in mind is some kind of accounting, to filter out greedy and nasty apps. If this is not the case, then I am lost. Could you please explain? -- Roman