From: Kevin Wolf <kwolf@redhat.com>
To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: Fam Zheng <famz@redhat.com>,
qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>,
Jeff Cody <jcody@redhat.com>,
Markus Armbruster <armbru@redhat.com>,
Eric Blake <eblake@redhat.com>,
qemu-block@nongnu.org, stefanha@redhat.com, pbonzini@redhat.com,
John Snow <jsnow@redhat.com>,
berrange@redhat.com, den@openvz.org
Subject: Re: [Qemu-devel] [PATCH v4 00/27] block: Lock images when opening
Date: Wed, 11 May 2016 13:56:05 +0200 [thread overview]
Message-ID: <20160511115605.GD4524@noname.str.redhat.com> (raw)
In-Reply-To: <20160511114841.GE1683@redhat.com>
Am 11.05.2016 um 13:48 hat Richard W.M. Jones geschrieben:
> While I remember there is another concern that doesn't seem to be
> addressed in this patch series. What happens when a guest is paused?
> I think exclusive locks should be converted to shared locks in that
> case, since (only while the guest is paused) it _is_ safe to fish
> around inside the guest's state. Of course the lock must be restored
> before the guest resumes.
I think it's still one of the cases where it's appropriate to require an
"I know what I'm doing" flag. In paused guests, you still don't
necessarily see the same contents as the guest does (because of guest
caches). Apart from that, things like block jobs and NBD servers keep
running even with a stopped VM.
The lock can only be dropped in cases where we can justify switching to
BDRV_O_INACTIVE, and I don't think a simple stop/cont should do this.
Kevin
next prev parent reply other threads:[~2016-05-11 11:56 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-10 2:50 [Qemu-devel] [PATCH v4 00/27] block: Lock images when opening Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 01/27] block: Add BDRV_O_NO_LOCK Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 02/27] qapi: Add lock-image in blockdev-add options Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 03/27] blockdev: Add and parse "lock-image" option for block devices Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 04/27] block: Introduce image file locking Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 05/27] block: Add bdrv_image_locked Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 06/27] block: Make bdrv_reopen_{commit, abort} private functions Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 07/27] block: Handle image locking during reopen Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 08/27] osdep: Add qemu_lock_fd and qemu_unlock_fd Fam Zheng
2016-05-10 7:54 ` Richard W.M. Jones
2016-05-10 8:57 ` Daniel P. Berrange
2016-05-10 9:06 ` Richard W.M. Jones
2016-05-10 9:20 ` Daniel P. Berrange
2016-05-11 0:48 ` Fam Zheng
2016-05-11 1:05 ` Fam Zheng
2016-05-11 9:01 ` Daniel P. Berrange
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 09/27] osdep: Introduce qemu_dup Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 10/27] raw-posix: Use qemu_dup Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 11/27] raw-posix: Implement .bdrv_lockf Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 12/27] gluster: " Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 13/27] qemu-io: Add "-L" option for BDRV_O_NO_LOCK Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 14/27] qemu-img: Add "-L" option to sub commands Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 15/27] qemu-img: Update documentation of "-L" option Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 16/27] qemu-nbd: Add "--no-lock/-L" option Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 17/27] block: Don't lock drive-backup target image in none mode Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 18/27] mirror: Disable image locking on target backing chain Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 19/27] qemu-iotests: 140: Disable image lock for qemu-io access Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 20/27] qemu-iotests: 046: Move version detection out from verify_io Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 21/27] qemu-iotests: Wait for QEMU processes before checking image in 091 Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 22/27] qemu-iotests: 030: Disable image lock when checking test image Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 23/27] iotests: 087: Disable image lock in cases where file is shared Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 24/27] iotests: Disable image locking in 085 Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 25/27] tests: Use null-co:// instead of /dev/null Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 26/27] block: Turn on image locking by default Fam Zheng
2016-05-10 2:50 ` [Qemu-devel] [PATCH v4 27/27] qemu-iotests: Add test case 153 for image locking Fam Zheng
2016-05-10 8:14 ` [Qemu-devel] [PATCH v4 00/27] block: Lock images when opening Richard W.M. Jones
2016-05-10 8:43 ` Richard W.M. Jones
2016-05-10 8:50 ` Daniel P. Berrange
2016-05-10 9:14 ` Kevin Wolf
2016-05-10 9:23 ` Daniel P. Berrange
2016-05-10 9:35 ` Kevin Wolf
2016-05-10 9:43 ` Daniel P. Berrange
2016-05-10 10:07 ` Kevin Wolf
2016-05-10 10:16 ` Richard W.M. Jones
2016-05-10 11:08 ` Kevin Wolf
2016-05-10 11:46 ` Richard W.M. Jones
2016-05-10 12:01 ` Kevin Wolf
2016-05-10 12:11 ` Richard W.M. Jones
2016-05-10 12:22 ` Daniel P. Berrange
2016-05-10 12:45 ` Kevin Wolf
2016-05-11 8:04 ` Markus Armbruster
2016-05-11 8:52 ` Daniel P. Berrange
2016-05-11 8:04 ` Fam Zheng
2016-05-11 9:28 ` Richard W.M. Jones
2016-05-11 10:03 ` Kevin Wolf
2016-05-10 10:29 ` Daniel P. Berrange
2016-05-10 11:14 ` Kevin Wolf
2016-05-10 10:02 ` Richard W.M. Jones
2016-05-11 11:48 ` Richard W.M. Jones
2016-05-11 11:56 ` Kevin Wolf [this message]
2016-05-12 1:07 ` Fam Zheng
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