From patchwork Sun Mar 17 16:33:34 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 13594683 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C223E17EF; Sun, 17 Mar 2024 16:33:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710693214; cv=none; b=LRwnwESWisD3MEpDIH3i/45N9OflsHM4yWro0ozTVAt1QXacIqMdO3wC6fXzdG1lMKuvFX7cCM/ffGY/PaVTt56xZlLahJ8xIbE1QqQlZKuB7zTrd4CpwYBdwE+Y/pMtaJyDz6gTJyPSCkMGATkT/jiSgQbuCYvMxIbmYppmd58= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710693214; c=relaxed/simple; bh=ONACup+laAfDNq7cx/v5Ol/o/ikJ0Zhm3Rp1DJWL5uc=; h=Date:Subject:From:To:Cc:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=DtvEai76COnwOOXixJxfPEd1C8HdduXDqtepmLFbeLpsasxemFitRZanLmBtsJ3Zn390t2+BHhU4YpLS1twbQlJ04Xh1v9Y9iRWd0DmcmnAt1X4bYBZbQiEYESxSsqXnmzBvHN1ioH/rS0CqALKOWzMKyvZw6leSIItDErhHUN4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hH9NWG7t; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hH9NWG7t" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 95DBEC433C7; Sun, 17 Mar 2024 16:33:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1710693214; bh=ONACup+laAfDNq7cx/v5Ol/o/ikJ0Zhm3Rp1DJWL5uc=; h=Date:Subject:From:To:Cc:In-Reply-To:References:From; b=hH9NWG7tsGU4g3x8pHr+OCkTFcuf+CwH8cqFZZDuoywHr0pJp4heTbptBkgdVe0d9 c8zJOExyfNbEOPkNsAwfp6NwAhPJW9xOBC0ByNvSbmSqu9Erl8t3nFbP+TS68MIsJA 42yXrnYK8YeyS5ukfDGDtGvHxdgSGO+Kv18AaC8pAAAKXUCSAx3mpM1y/F4CKZiSPr QkLtBKQ6+1xfx5aMIxPWibzz+OxXnINyMBpSr1IPQNlTogrMC6w8fJTgYeoCqXy/6w Qko8ETdIlNGGYR6QHJnXcVP/ZCatkxk1eNHccIOswmZ9jo4yiZmR3Y/nI04ajOQ+L6 ghDMF+D9964hg== Date: Sun, 17 Mar 2024 09:33:34 -0700 Subject: [PATCH 39/40] xfs: don't bother storing merkle tree blocks for zeroed data blocks From: "Darrick J. Wong" To: djwong@kernel.org, ebiggers@kernel.org, aalbersh@redhat.com Cc: linux-fsdevel@vger.kernel.org, fsverity@lists.linux.dev, linux-xfs@vger.kernel.org Message-ID: <171069246533.2684506.10607368938981182877.stgit@frogsfrogsfrogs> In-Reply-To: <171069245829.2684506.10682056181611490828.stgit@frogsfrogsfrogs> References: <171069245829.2684506.10682056181611490828.stgit@frogsfrogsfrogs> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: fsverity@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Darrick J. Wong Now that fsverity tells our merkle tree io functions about what a hash of a data block full of zeroes looks like, we can use this information to avoid writing out merkle tree blocks for sparse regions of the file. For verified gold master images this can save quite a bit of overhead. Signed-off-by: Darrick J. Wong Reviewed-by: Andrey Albershteyn --- fs/xfs/xfs_verity.c | 37 ++++++++++++++++++++++++++++++++++--- 1 file changed, 34 insertions(+), 3 deletions(-) diff --git a/fs/xfs/xfs_verity.c b/fs/xfs/xfs_verity.c index abd95bc1ba6e..ba96e7049f61 100644 --- a/fs/xfs/xfs_verity.c +++ b/fs/xfs/xfs_verity.c @@ -619,6 +619,20 @@ xfs_verity_read_merkle( xfs_verity_merkle_key_to_disk(&name, block->offset); error = xfs_attr_get(&args); + if (error == -ENOATTR) { + u8 *p; + unsigned int i; + + /* + * No attribute found. Synthesize a buffer full of the zero + * digests on the assumption that we elided them at write time. + */ + for (i = 0, p = new_mk->data; + i < block->size; + i += req->digest_size, p += req->digest_size) + memcpy(p, req->zero_digest, req->digest_size); + error = 0; + } if (error) goto out_new_mk; @@ -676,12 +690,29 @@ xfs_verity_write_merkle( .value = (void *)buf, .valuelen = size, }; - const char *p = buf + size - 1; + const char *p; + unsigned int i; - /* Don't store trailing zeroes. */ + /* + * If this is a block full of hashes of zeroed blocks, don't bother + * storing the block. We can synthesize them later. + */ + for (i = 0, p = buf; + i < size; + i += req->digest_size, p += req->digest_size) + if (memcmp(p, req->zero_digest, req->digest_size)) + break; + if (i == size) + return 0; + + /* + * Don't store trailing zeroes. Store at least one byte so that the + * block cannot be mistaken for an elided one. + */ + p = buf + size - 1; while (p >= (const char *)buf && *p == 0) p--; - args.valuelen = p - (const char *)buf + 1; + args.valuelen = max(1, p - (const char *)buf + 1); xfs_verity_merkle_key_to_disk(&name, pos); return xfs_attr_set(&args);