From patchwork Mon May 31 13:13:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 451103 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 A4E71C47080 for ; Mon, 31 May 2021 14:03:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8DB1D61942 for ; Mon, 31 May 2021 14:03:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232251AbhEaOFC (ORCPT ); Mon, 31 May 2021 10:05:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:37808 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232399AbhEaOCe (ORCPT ); Mon, 31 May 2021 10:02:34 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 899336194E; Mon, 31 May 2021 13:37:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1622468240; bh=5UMo4Vu4+ny9cwlNcrqTQOyBn8cjCWZaFGIgbUb9J/Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nledX1euTnC5fafNgiftAjjsNy5kbIee9AXOoCFeXl1FpAlSIy7+7BHhgO9ZNVxDG LZ7EdEwv8RxqKkQ/IXfjJQA4seENViKzvwZzRnvQUj9JuCuWEEwot4bJREPK4Ckken 2ngQcMSEnmegWxHl/3bttb3EbexCmlt/mAJlGrZw= 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 5.10 170/252] btrfs: return whole extents in fiemap Date: Mon, 31 May 2021 15:13:55 +0200 Message-Id: <20210531130703.787446522@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210531130657.971257589@linuxfoundation.org> References: <20210531130657.971257589@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 30cf917a58e9..81e98a457130 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4662,7 +4662,7 @@ int extent_fiemap(struct btrfs_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; @@ -4698,6 +4698,11 @@ int extent_fiemap(struct btrfs_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;