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 E2016C4332F for ; Tue, 7 Dec 2021 10:04:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5519F6B00A7; Tue, 7 Dec 2021 05:03:54 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 501886B00A8; Tue, 7 Dec 2021 05:03:54 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3F01F6B00A9; Tue, 7 Dec 2021 05:03:54 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0029.hostedemail.com [216.40.44.29]) by kanga.kvack.org (Postfix) with ESMTP id 309076B00A7 for ; Tue, 7 Dec 2021 05:03:54 -0500 (EST) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id EDF1718084BA7 for ; Tue, 7 Dec 2021 10:03:43 +0000 (UTC) X-FDA: 78890561526.06.40118D5 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf01.hostedemail.com (Postfix) with ESMTP id 7077940003 for ; Tue, 7 Dec 2021 10:03:43 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 0374E1FD2F; Tue, 7 Dec 2021 10:03:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1638871422; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=YwQ4bZdkWv3+Uy3+p3BVJaw61oSGu/aQTT0I5wfRf18=; b=Dqw67D3mF+cEHV+7m1y1Hp2YaRJcrsJe0ESB5PZc1jI4vdiqDOTKgjlJRvkYFhjjU3rvXs g9940Xjo5CsQcZAiRZZ3E0oEmjCenXDUy2WQeG1iW6MT0xpc3vRKnZCO14WN5y9VwDGDn3 paAFNrMNFHerOeu3Z/GYMdxsk1ZXdl0= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 018EEA3B91; Tue, 7 Dec 2021 10:03:40 +0000 (UTC) Date: Tue, 7 Dec 2021 11:03:40 +0100 From: Michal Hocko To: Matthew Wilcox Cc: Suren Baghdasaryan , akpm@linux-foundation.org, 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 v2 1/2] mm: protect free_pgtables with mmap_lock write lock in exit_mmap Message-ID: References: <20211124235906.14437-1-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: 7077940003 X-Stat-Signature: ndczepxbczm43bbxz9gt58b7i7k9nfzc Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=Dqw67D3m; spf=pass (imf01.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-HE-Tag: 1638871423-669913 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 Mon 06-12-21 18:52:28, Matthew Wilcox wrote: > On Mon, Dec 06, 2021 at 10:35:03AM -0800, Suren Baghdasaryan wrote: > > > Other than that looks OK to me. Maybe we want to add an explicit note > > > that vm_ops::close cannot take mmap_sem in any form. The changelog > > > should also mention that you have considered remove_vma and its previous > > > no MM locking assumption. You can argue that fput is async and close > > > callback shouldn't really need mmap_sem. > > > > Should I post another version of this patch with the patch description > > clarifying these points and additional comments as you suggested? > > fyi, vm_ops->close() is already called with the mmap_sem held for write > in __split_vma(). If that needs to be documented, it's a separate patch > because it's absolutely not a consequence of this patch. Agreed! We definitely want to document that. -- Michal Hocko SUSE Labs