From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELsoW0PQa/BJQeR6qlMHDp58GyZHOS5SnTscmOwnJPG2NtbC5W+pUvSS3qbRYqaewGCNBlLR ARC-Seal: i=1; a=rsa-sha256; t=1521484214; cv=none; d=google.com; s=arc-20160816; b=oT1Cz2DT4HR00IPDxmU1jXjHqBcnLkswD7u18fOTR69Izq+fxsvP23h1wi2KF3qcvb XSidglXIUjq9JEZwagD7lyihelmmMtH4FZn/RnKfDJOWt5cCKQqh4x/+ihUzJic4ZUY+ RcAJ60j0O1Q4r5E8YuE6pDfuMOx+wZwmwJNitVM88qkPgxoFRY9i38Q9XhZDocQ55hx4 5od7FUHJVBCKe+6smtHZ/3Vaxm2XU76Ac2mx6p9CsM2PLlI0CUcV2vaJftzWT7T8UBq9 I1nBe5CkFTGG+LXd7hGvaT2Aa1H72cyHp969tvtZxxQCBbDikQQ69/gYz5hEZxXHGgjd R7ug== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=mime-version:user-agent:references:in-reply-to:message-id:date :subject:cc:to:from:arc-authentication-results; bh=8CJN7NTR5WClvbjC8AJL/G5X5ZYkFP9URlxnrZnq9rg=; b=FdbXsaAsZ089fgV0I6cbOmKqxFUS0aNryFrZYGK2LO4PeYPr3l+LuHdRy+xau8aIXO eWPuKRF9C1bnxqbOomL/MsfAodN09u5I6XIoNk8UrCawzuQ1NFr8ENAQci4L0Hh7Z+wn asu0Jl5cnfcRdzdlQBXuS9MVJOgLNVbTEzc3tc7Nvza9StruM5LVn5ThSyE+0DA06P9c +MQ7NFYldBr7//hlrkp2cSF6Xtx3BicP/9Qbe1cER8XarHQaZ/yAS+xbOUMqWo/xgAeG P2i5LxtY+pfaBaUJL8Z53bfCTLccehKj8+Z0ooi+605OirmSmMHQm1DUsPeM3imtditr fIGQ== ARC-Authentication-Results: i=1; mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning gregkh@linuxfoundation.org does not designate 90.92.61.202 as permitted sender) smtp.mailfrom=gregkh@linuxfoundation.org From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Edmund Nadolski , David Sterba Subject: [PATCH 4.14 31/41] btrfs: add missing initialization in btrfs_check_shared Date: Mon, 19 Mar 2018 19:08:31 +0100 Message-Id: <20180319180734.271249639@linuxfoundation.org> X-Mailer: git-send-email 2.16.2 In-Reply-To: <20180319180732.195217948@linuxfoundation.org> References: <20180319180732.195217948@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-LABELS: =?utf-8?b?IlxcU2VudCI=?= X-GMAIL-THRID: =?utf-8?q?1595391831494126893?= X-GMAIL-MSGID: =?utf-8?q?1595391831494126893?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.14-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 @@ -1496,6 +1496,7 @@ int btrfs_check_shared(struct btrfs_root if (!node) break; bytenr = node->val; + shared.share_count = 0; cond_resched(); }