On Wed, Sep 06, 2017 at 12:19:05PM +0200, Kevin Wolf wrote:
> Am 06.09.2017 um 10:50 hat Richard W.M. Jones geschrieben:
> > Commit 16b48d5d66d2 ("file-posix: Add 'locking' option") added this
> > option, but as it was not documented in the -help output it was not
> > easily possible to tell if a particular qemu binary supports it.
> >
> > Signed-off-by: Richard W.M. Jones <rjo...@redhat.com>
> > ---
> > qemu-options.hx | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index 9f6e2adfff..f8f95eb498 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -796,7 +796,7 @@ DEF("drive", HAS_ARG, QEMU_OPTION_drive,
> > "
> > [,cache=writethrough|writeback|none|directsync|unsafe][,format=f]\n"
> > " [,serial=s][,addr=A][,rerror=ignore|stop|report]\n"
> > "
> > [,werror=ignore|stop|report|enospc][,id=name][,aio=threads|native]\n"
> > - " [,readonly=on|off][,copy-on-read=on|off]\n"
> > + "
> > [,readonly=on|off][,copy-on-read=on|off][,locking=off|auto|on]\n"
> > " [,discard=ignore|unmap][,detect-zeroes=on|off|unmap]\n"
> > " [[,bps=b]|[[,bps_rd=r][,bps_wr=w]]]\n"
> > " [[,iops=i]|[[,iops_rd=r][,iops_wr=w]]]\n"
>
> 'locking' is a driver-specific option and not universally available for
> all images, so it shouldn't be included here.
Indeed this patch is wrong, please ignore it.
However I couldn't work out the incantation to disable locking for a
qcow2 overlay backed by a file which is locked by another qemu
process:
...
-drive
file=/home/rjones/d/libguestfs/tmp/libguestfsSOXEiU/overlay1,cache=unsafe,format=qcow2,file.locking=off,id=hd0,if=none
\
-device scsi-hd,drive=hd0 \
...
qemu-system-x86_64: -device scsi-hd,drive=hd0: Failed to get shared "write"
lock
Is another process using the image?
...
I'm guessing I need another level of indirection to get to the backing
file, but file.file.locking=off did not work either.
I think the error message there is wrong as well since it doesn't
refer to the right command line option nor tell you which file is
locked.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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