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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 768A2C43331 for ; Thu, 26 Mar 2020 18:09:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3723420714 for ; Thu, 26 Mar 2020 18:09:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="uLrXxifG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3723420714 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E104E6B006C; Thu, 26 Mar 2020 14:09:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DC1CB6B006E; Thu, 26 Mar 2020 14:09:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C8A3D6B0070; Thu, 26 Mar 2020 14:09:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0054.hostedemail.com [216.40.44.54]) by kanga.kvack.org (Postfix) with ESMTP id AD9176B006C for ; Thu, 26 Mar 2020 14:09:20 -0400 (EDT) Received: from smtpin11.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id EEF319991 for ; Thu, 26 Mar 2020 18:09:20 +0000 (UTC) X-FDA: 76638300480.11.able82_175e55711da3b X-HE-Tag: able82_175e55711da3b X-Filterd-Recvd-Size: 3476 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf26.hostedemail.com (Postfix) with ESMTP for ; Thu, 26 Mar 2020 18:09:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=oGl3kyUUBo3pRyuKgQ0JM7kMCAak5k4pqUHDa2g2cJ8=; b=uLrXxifGT4O7snJNYyN4C7LkQy w9lZQ13zOq5kYBQEfor5TL9Ogk5wydcZJeHh39p05ZPMzQmZrrCXW4Xb/11m4XeAfY2VdDr5zecKF wz2EvCPMLd4lJrAd4FmSBzCHVMQty+jT3bwDbkNEyVb7fJyr3AvFClfij9Jg+qi8+Gp2DKe9TjtNG F8jGRx6EEF2XWR8gkcRNYww3T55LfqttfEuR9Mz8tN/FTKW1sEBL/qYkSXD77h+XG6YuMR54oU6IP wnvXJVSDC40sQk6JxLVlaZC32L80q0fGj5sVwNWIJKBBG093m9csTdbRSBFx8m8izByTHHlsxf8U3 ixNbDVdQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jHWwO-0007ev-UO; Thu, 26 Mar 2020 18:09:16 +0000 Date: Thu, 26 Mar 2020 11:09:16 -0700 From: Matthew Wilcox To: Jason Gunthorpe Cc: Michel Lespinasse , Andrew Morton , linux-mm , LKML , Peter Zijlstra , Laurent Dufour , Vlastimil Babka , Liam Howlett , Jerome Glisse , Davidlohr Bueso , David Rientjes , Hugh Dickins , Ying Han Subject: Re: [PATCH 1/8] mmap locking API: initial implementation as rwsem wrappers Message-ID: <20200326180916.GL22483@bombadil.infradead.org> References: <20200326070236.235835-1-walken@google.com> <20200326070236.235835-2-walken@google.com> <20200326175644.GN20941@ziepe.ca> <20200326180621.GK22483@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200326180621.GK22483@bombadil.infradead.org> 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 Thu, Mar 26, 2020 at 11:06:21AM -0700, Matthew Wilcox wrote: > On Thu, Mar 26, 2020 at 02:56:44PM -0300, Jason Gunthorpe wrote: > > On Thu, Mar 26, 2020 at 12:02:29AM -0700, Michel Lespinasse wrote: > > > > > +static inline bool mmap_is_locked(struct mm_struct *mm) > > > +{ > > > + return rwsem_is_locked(&mm->mmap_sem) != 0; > > > +} > > > > I've been wondering if the various VM_BUG(rwsem_is_locked()) would be > > better as lockdep expressions? Certainly when lockdep is enabled it > > should be preferred, IMHO. > > > > So, I think if inlines are to be introduced this should be something > > similar to netdev's ASSERT_RTNL which seems to have worked well. > > > > Maybe ASSERT_MMAP_SEM_READ/WRITE/HELD() and do the VM_BUG or > > lockdep_is_held as appropriate? > > I'd rather see lockdep_assert_held() used directly rather than have > a wrapper. This API includes options to check for it beind explicitly > held for read/write/any, which should be useful. ... oh, but that requires naming the lock, which we're trying to get away from. I guess we need a wrapper, but yes, by all means, let's level it up to put the VM_BUG_ON inside the wrapper, as that means we can get the mm dumped everywhere, rather than just the few places that have done VM_BUG_ON_MM instead of plain VM_BUG_ON.