From mboxrd@z Thu Jan 1 00:00:00 1970 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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 377A4C433DF for ; Mon, 29 Jun 2020 21:56:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D1F020760 for ; Mon, 29 Jun 2020 21:56:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593467785; bh=ENgkJVTolnCjsYCFo4x7kLx6RHWaOF/1KVZMARmqOnI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=QI58S3DgNqcE966tsQnjjx3bUUwVYKwVIuNQVEQ9lpmX4PYaAr/5KhuA3UY61ooYb H9Oh8jY3QH6EK1meOEVyFc/t1qmpm1sJrRQgqYIAcbhSvvBhlJF3mVKnbDsRkr7jr4 CxDlCwNcIsDRT0pYMvWLQhzgqDi5XoyGxGnrP5nc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404678AbgF2V4Y (ORCPT ); Mon, 29 Jun 2020 17:56:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:56814 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726539AbgF2Sfb (ORCPT ); Mon, 29 Jun 2020 14:35:31 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5EEF0247AF; Mon, 29 Jun 2020 15:21:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593444114; bh=ENgkJVTolnCjsYCFo4x7kLx6RHWaOF/1KVZMARmqOnI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0U0fsl1q1b6UvByWqAqwnu3EsnYaiPmSNUrD3GyXN7j48EuSbPDLDgPsPc2A56i2I xUYUh9gJIy0E/I7V3ci806ZuPStCTOW0u+6LO78p5rL0+RoPkROLRrvb6CrCGxw8wh yFQqy/9sIigjxQwq2xGugXSLPOVop8lXZ3lwtn+M= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Filipe Manana , David Sterba , Greg Kroah-Hartman Subject: [PATCH 5.7 225/265] btrfs: fix hang on snapshot creation after RWF_NOWAIT write Date: Mon, 29 Jun 2020 11:17:38 -0400 Message-Id: <20200629151818.2493727-226-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200629151818.2493727-1-sashal@kernel.org> References: <20200629151818.2493727-1-sashal@kernel.org> MIME-Version: 1.0 X-KernelTest-Patch: http://kernel.org/pub/linux/kernel/v5.x/stable-review/patch-5.7.7-rc1.gz X-KernelTest-Tree: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git X-KernelTest-Branch: linux-5.7.y X-KernelTest-Patches: git://git.kernel.org/pub/scm/linux/kernel/git/stable/stable-queue.git X-KernelTest-Version: 5.7.7-rc1 X-KernelTest-Deadline: 2020-07-01T15:14+00:00 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Filipe Manana commit f2cb2f39ccc30fa13d3ac078d461031a63960e5b upstream. If we do a successful RWF_NOWAIT write we end up locking the snapshot lock of the inode, through a call to check_can_nocow(), but we never unlock it. This means the next attempt to create a snapshot on the subvolume will hang forever. Trivial reproducer: $ mkfs.btrfs -f /dev/sdb $ mount /dev/sdb /mnt $ touch /mnt/foobar $ chattr +C /mnt/foobar $ xfs_io -d -c "pwrite -S 0xab 0 64K" /mnt/foobar $ xfs_io -d -c "pwrite -N -V 1 -S 0xfe 0 64K" /mnt/foobar $ btrfs subvolume snapshot -r /mnt /mnt/snap --> hangs Fix this by unlocking the snapshot lock if check_can_nocow() returned success. Fixes: edf064e7c6fec3 ("btrfs: nowait aio support") CC: stable@vger.kernel.org # 4.14+ Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/file.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 719e68ab552c5..484803f8b2290 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1922,6 +1922,8 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb, inode_unlock(inode); return -EAGAIN; } + /* check_can_nocow() locks the snapshot lock on success */ + btrfs_drew_write_unlock(&root->snapshot_lock); } current->backing_dev_info = inode_to_bdi(inode); -- 2.25.1