On 04/01/2016 02:37 AM, Wouter Verhelst wrote: > Hi, > > Thanks, applied. > > On Thu, Mar 31, 2016 at 04:02:05PM +0300, Denis V. Lunev wrote: >> From: Pavel Borzenkov <pborzen...@virtuozzo.com> >> >> There exist some cases when a client knows that the data it is going to >> write is all zeroes. Such cases include mirroring or backing up a device >> implemented by a sparse file. >> >> With current NBD command set, the client has to issue NBD_CMD_WRITE >> command with zeroed payload and transfer these zero bytes through the >> wire. The server has to write the data onto disk, effectively denying >> the sparseness. >>
>> + >> +- bit 1, `NBD_CMD_MAY_TRIM`; defined by the experimental `WRITE_ZEROES` >> + extension; see below. Hmm, we had an unfinished conversation about whether the default sense of this bit should be reversed. I'll propose a followup patch, now that the original has been merged. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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