From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48203) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aqGoO-00060G-CG for qemu-devel@nongnu.org; Wed, 13 Apr 2016 05:10:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aqGoN-0001kp-Dy for qemu-devel@nongnu.org; Wed, 13 Apr 2016 05:10:12 -0400 From: Fam Zheng Date: Wed, 13 Apr 2016 17:09:49 +0800 Message-Id: <1460538604-12132-1-git-send-email-famz@redhat.com> Subject: [Qemu-devel] [PATCH for-2.7 00/15] block: Lock images when opening List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Max Reitz , Jeff Cody , Markus Armbruster , Eric Blake , John Snow , qemu-block@nongnu.org, berrange@redhat.com, pbonzini@redhat.com, den@openvz.org Too many troubles have been caused by two processes writing to the same image unexpectedly. This series introduces automatical image locking into QEMU to avoid such tragedy. With this, the user won't be able to open the image from two processes (e.g. using qemu-img when the image is attached to the guest). Underneath is the fcntl syscall that locks the local file, similar to what is already used in libvirt virtlockd. Also because of that, we cannot directly apply fcntl lock on the image file itself, instead we open and lock "/var/tmp/.qemu-$sha1.lock", where $sha1 is derived from the image's full path as in realpath(3). This mechanism should be equally useful for the single host case, and it doesn't conflict with virtlockd when managed by libvirt. The alternative file locking API on Linux, flock(2), cannot protect host NFS mount points, so it's not used. Gluster locking is also implemented wrapping glfs_posix_lock in patch 6. It's only lightly tested. All other drivers that don't implement .bdrv_lockf are always permissive and does no checking. In the future, the intention is that image format drivers that introduce locking mechanisms could also fit into this API. The first 6 patches define the internal and external interfaces, and implement the image locking. Patch 7 adds an option in qemu-io to allow disabling the lock, for testing purpose. Patches 8 - 14 fixes the potential failures of test cases where multiple processes may open the image concurrently. Finally the default behavior is switched to on in patch 15. Fam Zheng (15): block: Add BDRV_O_NO_LOCK qapi: Add lock-image in blockdev-add options blockdev: Add and parse "lock-image" option for block devices block: Introduce image file locking interface raw-posix: Implement .bdrv_lockf gluster: Implement .bdrv_lockf qemu-io: Add "-L" option for BDRV_O_NO_LOCK qemu-iotests: 140: Disable image lock for qemu-io access qemu-iotests: 046: Move version detection out from verify_io qemu-iotests: Fix lock-image for shared disk in test case 091 qemu-iotests: Disable image lock when checking test image qemu-iotests: 051: Disable image lock in the command line ahci-test: Specify "lock-image=off" in CLI ide-test: Specify "lock-image=off" in command lines block: Turn on image locking by default block.c | 25 +++++++++++ block/gluster.c | 34 +++++++++++++++ block/raw-posix.c | 97 +++++++++++++++++++++++++++++++++++++++++++ blockdev.c | 8 ++++ include/block/block.h | 9 ++++ include/block/block_int.h | 5 +++ qapi/block-core.json | 6 ++- qemu-io.c | 22 +++++++++- tests/ahci-test.c | 16 +++++-- tests/ide-test.c | 5 ++- tests/qemu-iotests/030 | 2 +- tests/qemu-iotests/046 | 22 +++++----- tests/qemu-iotests/051 | 2 +- tests/qemu-iotests/051.out | 10 ++--- tests/qemu-iotests/051.pc.out | 10 ++--- tests/qemu-iotests/091 | 4 +- tests/qemu-iotests/140 | 2 +- 17 files changed, 245 insertions(+), 34 deletions(-) -- 2.8.0