Re: [Qemu-devel] [PATCH v3 0/8] block: Ignore loosening perm restrictions failures

[Eric Blake]

On 5/22/19 1:37 PM, Max Reitz wrote:

>> I don't know if there is an easy way to warn for normal users, but
>> silence the warnings if run under test setups to keep 'make check'
>> output unchanged (I know we've silenced warnings in the past when we
>> detect we are running qtest, but this isn't necessarily the same setup).
>>  So not a show-stopper for me.
> 
> Hm.  That doesn’t sound too bad.  I don’t think there is an easy way to
> silence the warning in qemu, but we might be able to just modify the test.
> 
> But I don’t even know whether the warnings are even useful or whether
> they would just confuse users more than anything.  So far, every case I
> know where loosening restrictions failed was because the file is just
> gone completely.  The only purpose of a warning is to show the user that
> qemu might have locks on the file that it doesn’t need, so they will
> know what’s up if they try to open the file in another qemu instance in
> a way that should normally work but suddenly doesn’t.  But if the file’s
> just gone, you can’t open it in another qemu, so I don’t even know
> whether there’s actually any point in warning.

Good point - if we unlink()ed the file, we can't loosen permissions, but
neither can anyone else open() it to collide with us :)

A network connection going down is a bit harder to justify (it might
come back up), but I think it still fits the bill (if we can't loosen
permissions, who else can interfere with us?)

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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