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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1709C433F5 for ; Fri, 24 Sep 2021 20:11:50 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 66ABE60EB6 for ; Fri, 24 Sep 2021 20:11:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 66ABE60EB6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id F0336900002; Fri, 24 Sep 2021 16:11:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EB19E6B0072; Fri, 24 Sep 2021 16:11:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DC79F900002; Fri, 24 Sep 2021 16:11:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0227.hostedemail.com [216.40.44.227]) by kanga.kvack.org (Postfix) with ESMTP id C99696B0071 for ; Fri, 24 Sep 2021 16:11:49 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 8A5EA39F50 for ; Fri, 24 Sep 2021 20:11:49 +0000 (UTC) X-FDA: 78623562738.24.DE94350 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf02.hostedemail.com (Postfix) with ESMTP id 1803B7001A08 for ; Fri, 24 Sep 2021 20:11:48 +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=7ncpmpQORtbSOxGAPueW+IXlEjJ+gZin6hmVmI/YRoo=; b=dGGkic4Lh01v+IinitCaZlfNiX d4rAidh/lyoGoYykLzOH+ZqCCDk8Rd9+U2sykPbWJ+M502s992XVMWRrHJybdQSfooRjBHScy+C1w OKKUm9gLECJ+3AVuiglpMi9jdz+DFjznSAMmp8qs0tMCPqwAVo2apHHBTTjQGk78PJMJcQgV5QCuD 43CmIgXIofEmyz19muuu45gg72RzzbAl5/IYVPVZIGoGw8CxVNi+llf3/o2l4nVRu5wzKaB7dmwJs DD954+B29YKp0MmWLo+gVjrbEzcCft43S2m0mnbwZnG0i4qYwWdQX6OaYnUHOrOWvtoK4Chx6PpaF VimTJydw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1mTrWC-007YNw-EY; Fri, 24 Sep 2021 20:10:11 +0000 Date: Fri, 24 Sep 2021 21:10:00 +0100 From: Matthew Wilcox To: David Howells Cc: hch@lst.de, trond.myklebust@primarydata.com, "Darrick J. Wong" , Ilya Dryomov , Jeff Layton , ceph-devel@vger.kernel.org, Steve French , linux-cifs@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, darrick.wong@oracle.com, viro@zeniv.linux.org.uk, torvalds@linux-foundation.org, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/9] mm: Add 'supports' field to the address_space_operations to list features Message-ID: References: <163250387273.2330363.13240781819520072222.stgit@warthog.procyon.org.uk> <163250389458.2330363.17234460134406104577.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <163250389458.2330363.17234460134406104577.stgit@warthog.procyon.org.uk> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 1803B7001A08 X-Stat-Signature: qc1t7iyuypu9hq1aqps5jsi7xyxzkew5 Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=dGGkic4L; 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: 1632514308-948365 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 Fri, Sep 24, 2021 at 06:18:14PM +0100, David Howells wrote: > Rather than depending on .direct_IO to point to something to indicate that > direct I/O is supported, add a 'supports' bitmask that we can test, since > we only need one bit. Why would you add mapping->aops->supports instead of using one of the free bits in mapping->flags? enum mapping_flags in pagemap.h. It could also be a per-fs flag, or per-sb flag, but it's fewer dereferences at check time if it's in mapping->flags.