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x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=linuxfoundation.org header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1032217AbeCSSd0 (ORCPT ); Mon, 19 Mar 2018 14:33:26 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:54418 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1032208AbeCSSdX (ORCPT ); Mon, 19 Mar 2018 14:33:23 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Edmund Nadolski , David Sterba Subject: [PATCH 4.15 33/52] btrfs: add missing initialization in btrfs_check_shared Date: Mon, 19 Mar 2018 19:08:31 +0100 Message-Id: <20180319180736.877316375@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180319180734.976730813@linuxfoundation.org> References: <20180319180734.976730813@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Edmund Nadolski commit 18bf591ba9753e3e5ba91f38f756a800693408f4 upstream. This patch addresses an issue that causes fiemap to falsely report a shared extent. The test case is as follows: xfs_io -f -d -c "pwrite -b 16k 0 64k" -c "fiemap -v" /media/scratch/file5 sync xfs_io -c "fiemap -v" /media/scratch/file5 which gives the resulting output: wrote 65536/65536 bytes at offset 0 64 KiB, 4 ops; 0.0000 sec (121.359 MiB/sec and 7766.9903 ops/sec) /media/scratch/file5: EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS 0: [0..127]: 24576..24703 128 0x2001 /media/scratch/file5: EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS 0: [0..127]: 24576..24703 128 0x1 This is because btrfs_check_shared calls find_parent_nodes repeatedly in a loop, passing a share_check struct to report the count of shared extent. But btrfs_check_shared does not re-initialize the count value to zero for subsequent calls from the loop, resulting in a false share count value. This is a regressive behavior from 4.13. With proper re-initialization the test result is as follows: wrote 65536/65536 bytes at offset 0 64 KiB, 4 ops; 0.0000 sec (110.035 MiB/sec and 7042.2535 ops/sec) /media/scratch/file5: EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS 0: [0..127]: 24576..24703 128 0x1 /media/scratch/file5: EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS 0: [0..127]: 24576..24703 128 0x1 which corrects the regression. Fixes: 3ec4d3238ab ("btrfs: allow backref search checks for shared extents") Signed-off-by: Edmund Nadolski [ add text from cover letter to changelog ] Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/backref.c | 1 + 1 file changed, 1 insertion(+) --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -1509,6 +1509,7 @@ int btrfs_check_shared(struct btrfs_root if (!node) break; bytenr = node->val; + shared.share_count = 0; cond_resched(); }