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 C09FCC433F5 for ; Wed, 8 Dec 2021 15:02:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 242CE6B0072; Wed, 8 Dec 2021 10:01:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1F2BF6B0073; Wed, 8 Dec 2021 10:01:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0BACA6B0074; Wed, 8 Dec 2021 10:01:59 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay037.a.hostedemail.com [64.99.140.37]) by kanga.kvack.org (Postfix) with ESMTP id F308F6B0072 for ; Wed, 8 Dec 2021 10:01:58 -0500 (EST) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay13.hostedemail.com (Postfix) with ESMTP id BB87460BE2 for ; Wed, 8 Dec 2021 15:01:48 +0000 (UTC) X-FDA: 78894941496.02.5AABFB9 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf02.hostedemail.com (Postfix) with ESMTP id EB1918002A for ; Wed, 8 Dec 2021 15:01:45 +0000 (UTC) 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=VH4twn5IAvnExuTGhr4b1JpOpGzuAOGbSYErzKxVLI4=; b=YX2XGllthBaVbk6S+fBCAUjq62 dC+4k2DcLhAEA/4LcTL7GkITJ4Npgjgm4I0/04GrcedcC9WlKZBC1g/z9egXtl97/RipbzVrraste tjEFxv9579TWkW3xDJCN+rv7FzvWYlDDMu3zr0iS7oI5kWMhZcgHsbfqVwT30mt7/RNNETh1A1ykX ecF979xuR95BH7pc57IIQS9smIJO5WfgI7ooHPYzBkPmNRrrAX9JDnSVemnplEaCIw3e0dxCN6ur0 IqGLPnA/mUL9kZdE3mkTMgCgEioneGdr+fqMOCilj8F7qG760wDxXsU30Xbf2HnXazJL8SQzEtDOI FUKdf9tg==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1muyRg-008VyL-R2; Wed, 08 Dec 2021 15:01:24 +0000 Date: Wed, 8 Dec 2021 15:01:24 +0000 From: Matthew Wilcox To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, mhocko@kernel.org, mhocko@suse.com, rientjes@google.com, hannes@cmpxchg.org, guro@fb.com, riel@surriel.com, minchan@kernel.org, kirill@shutemov.name, aarcange@redhat.com, christian@brauner.io, hch@infradead.org, oleg@redhat.com, david@redhat.com, jannh@google.com, shakeelb@google.com, luto@kernel.org, christian.brauner@ubuntu.com, fweimer@redhat.com, jengelh@inai.de, timmurray@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v3 1/2] mm: protect free_pgtables with mmap_lock write lock in exit_mmap Message-ID: References: <20211207215031.2251719-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: EB1918002A X-Stat-Signature: wizhetg9f5sy8t46t9nc3f7b5coimgjf Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=YX2XGllt; spf=none (imf02.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-HE-Tag: 1638975705-160334 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, Dec 07, 2021 at 03:08:19PM -0800, Suren Baghdasaryan wrote: > > > /** > > > * @close: Called when the VMA is being removed from the MM. > > > * Context: Caller holds mmap_lock. > > BTW, is the caller always required to hold mmap_lock for write or it > *might* hold it? __do_munmap() might hold it for read, thanks to: if (downgrade) mmap_write_downgrade(mm); Should probably say: * Context: User context. May sleep. Caller holds mmap_lock. I don't think we should burden the implementor of the vm_ops with the knowledge that the VM chooses to not hold the mmap_lock under certain circumstances when it doesn't matter whether it's holding the mmap_lock or not.