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Re: [Qemu-devel] [PATCH v5 00/27] block: Lock images when opening
From: |
Richard W.M. Jones |
Subject: |
Re: [Qemu-devel] [PATCH v5 00/27] block: Lock images when opening |
Date: |
Tue, 24 May 2016 12:48:45 +0100 |
User-agent: |
Mutt/1.5.20 (2009-12-10) |
On Tue, May 17, 2016 at 03:35:09PM +0800, Fam Zheng wrote:
> v5: - Change "lock-image=on/off" to "lock-mode=exclusive/shared/off".
> Default is "lock-mode=exclusive" to exclusively lock RW images and
> shared
> lock RO images; with lock-mode="shared", RW images are shared locked
> too;
> lock-mode=off turns off image locking completely.
> - Use F_OFD_SETLK fcntl so that close/dup on different fds are not a
> problem.
> - Update test cases.
My comments after testing this patch set:
* It's not possible to tell from the `qemu -help' output that this
binary supports the lock-mode option. Please add this to the -help
output (under `-drive') so we can detect it in qemu.
* I patched libguestfs to add the `lock-image=off' flag when the drive
is added readonly. This permits libguestfs to read live guests. I
also checked that writing to live guests is now forbidden, and it
is, which is good. In the write-to-live-guest case libguestfs will
now fail with:
qemu-system-x86_64: -drive
file=/var/tmp/centos-6.img,cache=writeback,id=hd0,if=none: Failed to lock image
So definitely we need this option to be reflected in the -help output.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines. Supports shell scripting,
bindings from many languages. http://libguestfs.org
- [Qemu-devel] [PATCH v5 22/27] qemu-iotests: 030: Disable image lock when checking test image, (continued)
- [Qemu-devel] [PATCH v5 22/27] qemu-iotests: 030: Disable image lock when checking test image, Fam Zheng, 2016/05/17
- [Qemu-devel] [PATCH v5 24/27] iotests: Disable image locking in 085, Fam Zheng, 2016/05/17
- [Qemu-devel] [PATCH v5 26/27] block: Turn on image locking by default, Fam Zheng, 2016/05/17
- [Qemu-devel] [PATCH v5 25/27] tests: Use null-co:// instead of /dev/null, Fam Zheng, 2016/05/17
- [Qemu-devel] [PATCH v5 27/27] qemu-iotests: Add test case 153 for image locking, Fam Zheng, 2016/05/17
- Re: [Qemu-devel] [PATCH v5 00/27] block: Lock images when opening,
Richard W.M. Jones <=