Re: [PATCH] file-posix: detect the lock using the real file

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Dec 08, 2020 at 03:38:22PM +0100, Kevin Wolf wrote:
> Am 08.12.2020 um 13:59 hat Li Feng geschrieben:
> > This patch addresses this issue:
> > When accessing a volume on an NFS filesystem without supporting the file lock,
> > tools, like qemu-img, will complain "Failed to lock byte 100".
> > 
> > In the original code, the qemu_has_ofd_lock will test the lock on the
> > "/dev/null" pseudo-file. Actually, the file.locking is per-drive property,
> > which depends on the underlay filesystem.
> > 
> > In this patch, make the 'qemu_has_ofd_lock' with a filename be more generic
> > and reasonable.
> > 
> > Signed-off-by: Li Feng <fengli@smartx.com>
> 
> Do you know any way how I could configure either the NFS server or the
> NFS client such that locking would fail? For any patch related to this,
> it would be good if I could even test the scenario.

One could write a qtest that uses an LD_PRELOAD to replace the standard
glibc fcntl() function with one that returns an error for locking commands.

Regards,
Daniel
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