Re: [Qemu-devel] [Libguestfs] [PATCH] tests: regressions: make test-big-heap use a temporary empty file

[Pino Toscano <ptoscano@redhat.com>]

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On Wednesday, 21 March 2018 14:45:38 CET Eric Blake wrote:
> [adding qemu lists]
> 
> On 03/21/2018 07:51 AM, Richard W.M. Jones wrote:
> > On Wed, Mar 21, 2018 at 01:44:17PM +0100, Pino Toscano wrote:
> >> Newer versions of qemu use file locking for the images by default, and
> >> apparently that does not work with /dev/null.  Since this test just
> >> calls qemu-img to get the format of an empty image, create a temporary
> >> one instead.
> > 
> > ACK, but feels like this is a bug in qemu-img to me.
> 
> You're right that file locking on a character device like /dev/null is 
> not going to work as expected, but is it a case where fcntl() actually 
> fails, or is it worse where the fcntl() claiming the locks "succeeds" 
> but doesn't do what we want?  That is, what were the actual error 
> messages you ran into?

$ qemu-img --version
qemu-img version 2.10.1(qemu-2.10.1-2.fc27)
Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers
$ qemu-img info /dev/null 
qemu-img: Could not open '/dev/null': Failed to get "consistent read" lock
Is another process using the image?

-- 
Pino Toscano

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