From: Daniel Berrange <1721788@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: [Qemu-devel] [Bug 1721788] Re: Failed to get shared "write" lock with 'qemu-img info'
Date: Fri, 06 Oct 2017 14:28:37 -0000 [thread overview]
Message-ID: <150730011794.1539.12869692950017908242.malone@chaenomeles.canonical.com> (raw)
In-Reply-To: 150729895903.22243.5921581973131047310.malonedeb@gac.canonical.com
The QEMU process that has the disk image open may be doing I/O that
causes qcow2 metadata to be changed. Such changes could confuse the
'qemu-img' process it is was reading the metadata at the same time it
was being changed, causing bad data to be printed or worse. So requiring
a write lock is the 'safe' thing to do for reliability in the worst
case. You can override this by passing '--force-share' arg though.
--
You received this bug notification because you are a member of qemu-
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https://bugs.launchpad.net/bugs/1721788
Title:
Failed to get shared "write" lock with 'qemu-img info'
Status in QEMU:
New
Bug description:
When running 'qemu-img info test.qcow2' while test.qcow2 is currently
used by a Qemu process, I get the error
qemu-img: Could not open 'test.qcow2': Failed to get shared "write"
lock.
Why does displaying information about a disk image need a write lock for the file?
Steps to reproduce:
qemu-img create -f qcow2 test.qcow2 10M
qemu-system-x86_64 -nographic -drive file=test.qcow2
qemu-img info test.qcow2
The above was tested with Qemu version 2.10.0
To manage notifications about this bug go to:
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next prev parent reply other threads:[~2017-10-06 14:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-06 14:09 [Qemu-devel] [Bug 1721788] [NEW] Failed to get shared "write" lock with 'qemu-img info' Jan Heidbrink
2017-10-06 14:28 ` Daniel Berrange [this message]
2017-10-06 14:28 ` Eric Blake
2017-10-06 14:30 ` [Qemu-devel] [Bug 1721788] " Daniel Berrange
2017-10-11 20:46 ` Liang Yan
2021-04-22 5:29 ` Thomas Huth
2021-04-22 8:14 ` Jan Heidbrink
2021-04-22 11:05 ` Max Reitz
2021-04-23 13:43 ` Jan Heidbrink
2022-04-19 14:35 ` Kaitlyn Lew
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