Re: [ANNOUNCE] Native Linux KVM tool v2

[Ingo Molnar]

* Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:

> On Thu, Jun 16, 2011 at 12:57:36PM +0300, Pekka Enberg wrote:
> > Uh-oh. Someone needs to apply this patch to sync_file_range():
> 
> There actually are a few cases where using it makes sense. [...]

Such as? I don't think apps can actually know whether disk blocks 
have been 'instantiated' by a particular filesystem or not, so the 
manpage:

   Some details
       None  of these operations write out the fileâs metadata.  Therefore, unless the appli-
       cation is strictly performing overwrites of already-instantiated  disk  blocks,  there
       are no guarantees that the data will be available after a crash.

is rather misleading. This is a dangerous (and rather pointless) 
syscall and this should be made much clearer in the manpage.

Thanks,

	Ingo
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