On 01/31/2017 10:36 AM, Alberto Garcia wrote: > On Tue 31 Jan 2017 05:31:32 PM CET, Eric Blake wrote: > >> Ideally, it would be nice to fix the block layer to allow larger >> requests (since we already have code to auto-fragment down to device >> limits, we should be able to rely on that code instead of having to >> duplicate artificial constraints everywhere else in the tree). But >> that's a bigger task, and this is a good patch in the interim. > > Related question: what's the largest request than a guest can > theoretically submit?
off_t supports up to 2^63 (not 2^64, because it is a signed type). Ideally, we should be constrained only by the disk size (as no one actually has 2^63 bytes of storage available), by using uint64_t offset AND length in all our APIs; but right now, we still have a lot of 32-bit length issues, and often signed length limiting us to 2^31 depending on the API. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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