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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0034FEB64D7 for ; Fri, 30 Jun 2023 03:48:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230462AbjF3DsM (ORCPT ); Thu, 29 Jun 2023 23:48:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229742AbjF3DsG (ORCPT ); Thu, 29 Jun 2023 23:48:06 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 46C2C2695; Thu, 29 Jun 2023 20:48:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=mLErujKCxnHxWmPdMQxMq1pzJ9BcSmvolBjr/rkB8IM=; b=AOx50gsTTRZJfWObn1a4I7aZWQ HkKBvjPWlOhSroaATP4aCv6wxMtpJdnbQSc6uLkBNu/MEoe/nT/tG+qNUzuCbXb5Fi+hveuLMactT 0bCvFBTK+1ghjbZJmoHEwYX4a/28B9HtXIHOUFP95UaIytwtahfkx+agHJdOjETACTWSXvCBEjyfW VO3zimcmN/g+byjx9HGVVwV5porjIlhNSfaSReqvm0qYN7qwnYiKBJF23MjLWf5g1fJF8+90pZkzo cew2yEm62L0UVKYC3iHk+vtoA7Z+RCpe0kWHbnQ5ryuKmcSrLvBElZkt0U1QHNzbxB0SPfe5G+WVe qTWDxpXQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qF56N-005OmN-3m; Fri, 30 Jun 2023 03:47:19 +0000 Date: Fri, 30 Jun 2023 04:47:19 +0100 From: Matthew Wilcox To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, peterx@redhat.com, ying.huang@intel.com, david@redhat.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v6 4/6] mm: change folio_lock_or_retry to use vm_fault directly Message-ID: References: <20230630020436.1066016-1-surenb@google.com> <20230630020436.1066016-5-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 29, 2023 at 08:45:39PM -0700, Suren Baghdasaryan wrote: > On Thu, Jun 29, 2023 at 8:36 PM Matthew Wilcox wrote: > > > > On Thu, Jun 29, 2023 at 07:04:33PM -0700, Suren Baghdasaryan wrote: > > > Change folio_lock_or_retry to accept vm_fault struct and return the > > > vm_fault_t directly. > > > > I thought we decided to call this folio_lock_fault()? > > > > > +static inline vm_fault_t folio_lock_or_retry(struct folio *folio, > > > + struct vm_fault *vmf) > > > { > > > might_sleep(); > > > - return folio_trylock(folio) || __folio_lock_or_retry(folio, mm, flags); > > > + return folio_trylock(folio) ? 0 : __folio_lock_or_retry(folio, vmf); > > > > No, don't use the awful ternary operator. The || form is used > > everywhere else. > > Ok, but folio_trylock() returns a boolean while folio_lock_or_retry > should return vm_fault_t. How exactly do you suggest changing this? > Something like this perhaps: > > static inline vm_fault_t folio_lock_or_retry(struct folio *folio, > struct vm_fault *vmf) > { > might_sleep(); > if (folio_trylock(folio)) > return 0; > return __folio_lock_or_retry(folio, mm, flags); > } > > ? I think the automatic casting would work, but I prefer what you've written here. > > > /* > > > * Return values: > > > - * true - folio is locked; mmap_lock is still held. > > > - * false - folio is not locked. > > > + * 0 - folio is locked. > > > + * VM_FAULT_RETRY - folio is not locked. > > > > I don't think we want to be so prescriptive here. It returns non-zero > > if the folio is not locked. The precise value is not something that > > callers should depend on. > > Ok, I'll change it to "non-zero" here. Thanks!