Re: It is safe to execute a fallocate on a opened and in-use file?

[Gionatan Danti <g.danti@assyoma.it>]

Il 10-06-2017 23:18 Darrick J. Wong ha scritto:
> 
> Yes, writes and fallocates are serialized with each other to avoid 
> corruption.
> 

Great. Is this behavior valid for all filesystem (ie: it is implemented 
on the VFS layer) or is it filesystem-specific?

> 
> How do you get qemu to announce the disk size change the guest?
> 

You can do that via virsh blockresize which, in turn, taps on qemu 
monitor (which can even be used directly, without libvirt intervention). 
 From virsh man page:

"blockresize domain path size
Resize a block device of domain while the domain is running, path 
specifies the absolute path of the block device; it corresponds to a 
unique target name (<target dev='name'/>) or source file (<source 
file='name'/>) for one of the disk devices attached to domain (see also 
domblklist for listing these names)."

Thanks.

> --D
> 
>> In general, how to consider concurrent metadata updates for the same
>> file/block? Should I expect file corruption, similar to concurrently 
>> writing
>> data to the same file/block?
>> 
>> Thanks.
>> 
>> --
>> Danti Gionatan
>> Supporto Tecnico
>> Assyoma S.r.l. - www.assyoma.it
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-- 
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8