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 29EB8C74A5B for ; Mon, 27 Mar 2023 00:57:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229892AbjC0A5j (ORCPT ); Sun, 26 Mar 2023 20:57:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229653AbjC0A5i (ORCPT ); Sun, 26 Mar 2023 20:57:38 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C0287421B; Sun, 26 Mar 2023 17:57:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; 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=Y4rrk/BoxyCld1nXBi3duNR/P4tM7eFuoP4ATdtR7tE=; b=BcaysuKG0nAGBS9JX5f7ngckEC Wsd6lWflVy5vwZSmvb/uAOaV3NSJ3ZdzuYUAOI7ZcEYNu3S1ZXJKqk609b2hIGSrnIjlTB1pG7JtC 2gd30KofRBnkcGZpXNGxhHZHWNC6le16zwBonD5JVtF1zpDmRudPPB7FhFlmra+WxrrIwRRZIUZ4/ YGgOg24lrDHBxbAS76zjax8TWyq7xBcdbgHTLphcUuG65kgQQ6Sh/qu1msMc1l+X1S9aYzmN5FxIU U/VEn4oF7zuesvCW4Twk2Qx/oTLo1v9EDwl7Q0kz0McXadbL2RGj/23bko5AJJZ+XRXxnpipWvT+7 WgYIj5Jw==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1pgbB0-009RIU-04; Mon, 27 Mar 2023 00:57:34 +0000 Date: Sun, 26 Mar 2023 17:57:33 -0700 From: Christoph Hellwig To: "Darrick J. Wong" Cc: Matthew Wilcox , Ritesh Harjani , Theodore Tso , Andreas Dilger , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 04/31] ext4: Convert ext4_finish_bio() to use folios Message-ID: References: <20230126202415.1682629-5-willy@infradead.org> <87ttyy1bz4.fsf@doe.com> <20230323145109.GA466457@frogsfrogsfrogs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230323145109.GA466457@frogsfrogsfrogs> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu, Mar 23, 2023 at 07:51:09AM -0700, Darrick J. Wong wrote: > Yes. Let's leave bufferheads in the legacy doo-doo-dooooo basement > instead of wasting more time on them. Ideally we'd someday run all the > filesystems through: > > bufferheads -> iomap with bufferheads -> iomap with folios -> iomap with > large folios -> retire to somewhere cheaper than Hawaii For a lot of the legacy stuff (and with that I don't mean ext4) we'd really need volunteers to do any work other than typo fixing and cosmetic cleanups. I suspect just dropping many of them is the only thing we can do long term. But even if we do the above for the data path for all file systems remaining in tree, we still have buffer_heads for metadata. And I think buffered_heads really are more or less the right abstraction there anyway. And for these existing file systems we also do not care about using large folios for metadata caching anyway. The only nasty part is that these buffer_heads use the same mapping as all block device access, so we'll need to find a way to use large folios for the block device mapping for the LBA size > page size case, while supporting buffer heads for those file systems. Nothing unsolvable, but a bit tricky.