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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 546B4C76188 for ; Wed, 5 Apr 2023 18:16:14 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4PsCW03r6Sz3f4n for ; Thu, 6 Apr 2023 04:16:12 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=REOOWtLg; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=139.178.84.217; helo=dfw.source.kernel.org; envelope-from=ebiggers@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=REOOWtLg; dkim-atps=neutral Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4PsCVr5Gpnz3chl for ; Thu, 6 Apr 2023 04:16:04 +1000 (AEST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4EC7B63D3A; Wed, 5 Apr 2023 18:16:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 710CAC433EF; Wed, 5 Apr 2023 18:16:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1680718561; bh=wiJeaBlTTUnHN5dRjU986tMd+hpSmAJjFn5myvsg4zA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=REOOWtLgQ9JDh9SSF6xoyg94oSouuHFnpL2v3YnQ3T2oBYSI6IMS8Hy8imtRKtDy1 cU3K/Iy3e/I3Q2+TSdKRafqsRNXapecZukPc1WANLn9sTP01Li50nyZ7qlCS5TCVJ+ 3cW7AZM1K/82Q6rN89XufLRWJRxkvNpgVxn/rDB2tRQwEAn32VY0qtyYqIT5Mhljtf O5whuuDDjSKbQwdJKsF8Nl8Wr8dqY9vgtd1lUYNpjci7tFUD9wHH4/61yvdWJlTH+K DtIew2Dd7HkelryBLbZ5MioiFh7yAV2qMaWKrH/687VXslb1Q2GI4zSjEhOMaWMwe0 NDlFE8RqYVveQ== Date: Wed, 5 Apr 2023 18:16:00 +0000 From: Eric Biggers To: "Darrick J. Wong" Subject: Re: [PATCH v2 21/23] xfs: handle merkle tree block size != fs blocksize != PAGE_SIZE Message-ID: References: <20230404145319.2057051-1-aalbersh@redhat.com> <20230404145319.2057051-22-aalbersh@redhat.com> <20230404163602.GC109974@frogsfrogsfrogs> <20230405160221.he76fb5b45dud6du@aalbersh.remote.csb> <20230405163847.GG303486@frogsfrogsfrogs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230405163847.GG303486@frogsfrogsfrogs> X-BeenThere: linux-erofs@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Linux EROFS file system List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: fsverity@lists.linux.dev, linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org, agruenba@redhat.com, Andrey Albershteyn , linux-f2fs-devel@lists.sourceforge.net, hch@infradead.org, cluster-devel@redhat.com, dchinner@redhat.com, rpeterso@redhat.com, jth@kernel.org, linux-erofs@lists.ozlabs.org, damien.lemoal@opensource.wdc.com, linux-btrfs@vger.kernel.org Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Sender: "Linux-erofs" On Wed, Apr 05, 2023 at 09:38:47AM -0700, Darrick J. Wong wrote: > > The merkle tree pages are dropped after verification. When page is > > dropped xfs_buf is marked as verified. If fs-verity wants to > > verify again it will get the same verified buffer. If buffer is > > evicted it won't have verified state. > > > > So, with enough memory pressure buffers will be dropped and need to > > be reverified. > > Please excuse me if this was discussed and rejected long ago, but > perhaps fsverity should try to hang on to the merkle tree pages that > this function returns for as long as possible until reclaim comes for > them? > > With the merkle tree page lifetimes extended, you then don't need to > attach the xfs_buf to page->private, nor does xfs have to extend the > buffer cache to stash XBF_VERITY_CHECKED. Well, all the other filesystems that support fsverity (ext4, f2fs, and btrfs) just cache the Merkle tree pages in the inode's page cache. It's an approach that I know some people aren't a fan of, but it's efficient and it works. We could certainly think about moving to a design where fs/verity/ asks the filesystem to just *read* a Merkle tree block, without adding it to a cache, and then fs/verity/ implements the caching itself. That would require some large changes to each filesystem, though, unless we were to double-cache the Merkle tree blocks which would be inefficient. So it feels like continuing to have the filesystem (not fs/verity/) be responsible for the cache is the best way to allow XFS to do things a bit differently, without regressing the other filesystems. I'm interested in hearing any other proposals, though. - Eric