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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6769E77187 for ; Wed, 18 Dec 2024 17:44:43 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 737B36B0083; Wed, 18 Dec 2024 12:44:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6E8966B0085; Wed, 18 Dec 2024 12:44:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5B0126B0088; Wed, 18 Dec 2024 12:44:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 3B9CF6B0083 for ; Wed, 18 Dec 2024 12:44:43 -0500 (EST) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id B7BB6B0394 for ; Wed, 18 Dec 2024 17:44:42 +0000 (UTC) X-FDA: 82908804510.14.4DDBD7B Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf24.hostedemail.com (Postfix) with ESMTP id A63D4180016 for ; Wed, 18 Dec 2024 17:44:36 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=DMiKqCHd; spf=none (imf24.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1734543865; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=6AKsDHa8OFbJ13ceQoyB8+HCYFVXtvagr3LUgXqZF+c=; b=uDDplAdNo78+bx7Arr7t9AgA3rO/akGyUN8BXu92lFi1E3aKMSnhiOVKonJqDHj73dH18R O1OhUZDw1Qu3pjfaOD1ZMiOROgQvr+f2O/Qjr1KW+Ewou4CTK2ChQaCvJ38LKY/RxYwHSH JB0PFxGYvIQsXv3LexakSFf8oTSIw3I= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1734543865; a=rsa-sha256; cv=none; b=Andn19eIPWvGNcsTUqwcsvM3x38uWZDSJBVWcCjvrBCN7Wcs7uD4PmrZ2IZjn7zfYzG9c8 vRacsZHegxByERE8Ap8YShokX+HypD35+KXflpTHp4Z7oNP6XN6yXLOObAL3EaFXUHZnLT OhbdWCTOxI21Cbon28tFEWlFqfZmIb0= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=DMiKqCHd; spf=none (imf24.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=6AKsDHa8OFbJ13ceQoyB8+HCYFVXtvagr3LUgXqZF+c=; b=DMiKqCHdIz7aJ4mIkP4E13B3OH B+YrsklM2VnF0I2XJEHNa5E5wUJ6CotOsnY9lWkfNvfESeIQCxPQsMzueJaaSIpP2tbDDtRxufq+X mfPo/5Z2CQy1SM63picLtapJZo6oUCgs8w0lzIoguJf8q8wInxvWVRpM0MmoU5I5Mb4zxXx6LIgTv Fni2PB271v1o+s2beEDaa9NlCWsFwOjqNFHMiadI6M2e+vwRnm4qTqb0/+GkVty8E0KHZb6hgsMar 193I8ZgEBzKiTu4wRC3lRJkjBuSPUpq8J/im3CyX33Si52Rh2Wj0orq+HWt9e8CaE3OeF6C/vylOA Nd5iFlrA==; Received: from 77-249-17-89.cable.dynamic.v4.ziggo.nl ([77.249.17.89] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tNy60-00000000NX4-35ov; Wed, 18 Dec 2024 17:44:29 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id A542130031E; Wed, 18 Dec 2024 18:44:28 +0100 (CET) Date: Wed, 18 Dec 2024 18:44:28 +0100 From: Peter Zijlstra To: Suren Baghdasaryan Cc: "Liam R. Howlett" , akpm@linux-foundation.org, willy@infradead.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v6 10/16] mm: replace vm_lock and detached flag with a reference count Message-ID: <20241218174428.GQ2354@noisy.programming.kicks-ass.net> References: <20241216213753.GD9803@noisy.programming.kicks-ass.net> <20241217103035.GD11133@noisy.programming.kicks-ass.net> <20241218094104.GC2354@noisy.programming.kicks-ass.net> <20241218100601.GI12500@noisy.programming.kicks-ass.net> <20241218161850.GG2354@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: A63D4180016 X-Stat-Signature: 6p4io941fxxqdfbwu8e1sa4db88d1g4n X-Rspam-User: X-HE-Tag: 1734543876-949105 X-HE-Meta: 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 RDg8r0vH XlfK7sf3YKrvJgm316PuoUxyxWSOnGG4isoFHRTizRAC2eqF2vWmKe4CWKS9qhGXN2bDjlnTA6FZ2uf+zDkRiEGVCh8RVAKbMU5bFhseKjJylEhGrkkfNJLfGyK4EQ+20/38RZYKvd6zWwrCTts0n1h4FZuzrzePviYf+v8B4YWm4OSmXIpC+jsldHU5t6NefHl9dGagNldR8gz0pYcR2Ht7HOKkJEDuT/7EwqS+mN0Y62zWJRE8XDX93oA== 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: List-Subscribe: List-Unsubscribe: On Wed, Dec 18, 2024 at 09:36:42AM -0800, Suren Baghdasaryan wrote: > > You will not. vms_complete_munmap_vmas() will call remove_vma() to > > remove PTEs IIRC, and if you do start_write() and detach() before > > dropping mmap_lock_write, you should be good. > > Ok, I think we will have to move mmap_write_downgrade() inside > vms_complete_munmap_vmas() to be called after remove_vma(). > vms_clear_ptes() is using vmas, so we can't move remove_vma() before > mmap_write_downgrade(). Why ?! vms_clear_ptes() and remove_vma() are fine where they are -- there is no concurrency left at this point. Note that by doing vma_start_write() inside vms_complete_munmap_vmas(), which is *after* the vmas have been unhooked from the mm, you wait for any concurrent user to go away. And since they're unhooked, there can't be any new users. So you're the one and only user left, and code is fine the way it is.