From patchwork Mon May 31 13:14:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 450994 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60CDCC47080 for ; Mon, 31 May 2021 14:25:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3F27F613AE for ; Mon, 31 May 2021 14:25:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233386AbhEaO1U (ORCPT ); Mon, 31 May 2021 10:27:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:48834 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233075AbhEaOZV (ORCPT ); Mon, 31 May 2021 10:25:21 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CB7F861A2B; Mon, 31 May 2021 13:46:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1622468792; bh=V6Ht5Q1d7BA+Esqjk6ydJwBvQnSAYZKpF8/BlSXnVyw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jKZ8Hhe9Ap0Ii2LylgUe6RiZrHYLWfbydB7aVqafKm50FfBuVU+kxqkMKL8bb4EEr MXbcDiC/tsPbbw8xH4aXnKYSSn/o3edcVteiN/OoyMckH3irsPUcCHzX4ioXiAooBC OKzMOuJNg5JYipmUlC8QcWU5o8c+YO5qUFmcpByA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Josef Bacik , Boris Burkov , David Sterba , Sasha Levin Subject: [PATCH 5.4 123/177] btrfs: return whole extents in fiemap Date: Mon, 31 May 2021 15:14:40 +0200 Message-Id: <20210531130652.173259255@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210531130647.887605866@linuxfoundation.org> References: <20210531130647.887605866@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Boris Burkov [ Upstream commit 15c7745c9a0078edad1f7df5a6bb7b80bc8cca23 ] `xfs_io -c 'fiemap ' ` can give surprising results on btrfs that differ from xfs. btrfs prints out extents trimmed to fit the user input. If the user's fiemap request has an offset, then rather than returning each whole extent which intersects that range, we also trim the start extent to not have start < off. Documentation in filesystems/fiemap.txt and the xfs_io man page suggests that returning the whole extent is expected. Some cases which all yield the same fiemap in xfs, but not btrfs: dd if=/dev/zero of=$f bs=4k count=1 sudo xfs_io -c 'fiemap 0 1024' $f 0: [0..7]: 26624..26631 sudo xfs_io -c 'fiemap 2048 1024' $f 0: [4..7]: 26628..26631 sudo xfs_io -c 'fiemap 2048 4096' $f 0: [4..7]: 26628..26631 sudo xfs_io -c 'fiemap 3584 512' $f 0: [7..7]: 26631..26631 sudo xfs_io -c 'fiemap 4091 5' $f 0: [7..6]: 26631..26630 I believe this is a consequence of the logic for merging contiguous extents represented by separate extent items. That logic needs to track the last offset as it loops through the extent items, which happens to pick up the start offset on the first iteration, and trim off the beginning of the full extent. To fix it, start `off` at 0 rather than `start` so that we keep the iteration/merging intact without cutting off the start of the extent. after the fix, all the above commands give: 0: [0..7]: 26624..26631 The merging logic is exercised by fstest generic/483, and I have written a new fstest for checking we don't have backwards or zero-length fiemaps for cases like those above. Reviewed-by: Josef Bacik Signed-off-by: Boris Burkov Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/extent_io.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 95205bde240f..eca3abc1a7cd 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4648,7 +4648,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, __u64 start, __u64 len) { int ret = 0; - u64 off = start; + u64 off; u64 max = start + len; u32 flags = 0; u32 found_type; @@ -4684,6 +4684,11 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, goto out_free_ulist; } + /* + * We can't initialize that to 'start' as this could miss extents due + * to extent item merging + */ + off = 0; start = round_down(start, btrfs_inode_sectorsize(inode)); len = round_up(max, btrfs_inode_sectorsize(inode)) - start;