On 07/17/2014 12:10 PM, John Ferlan wrote: > https://bugzilla.redhat.com/show_bug.cgi?id=1091866 > > Add a new boolean 'sparse'. This will be used by the logical backend > storage driver to determine whether the target volume is sparse or not > (also known by a snapshot or thin logical volume). Although setting sparse > to true at creation could be seen as duplicitous to setting during > virStorageBackendLogicalMakeVol() in case there are ever other code paths > between Create and FindLVs that need to know about the volume be sparse. > > Use the 'sparse' in a new virStorageBackendLogicalVolWipe() to decide whether > to attempt to wipe the logical volume or not. For now, I have found no > means to wipe the volume without writing to it. Writing to the sparse > volume causes it to be filled. A sparse logical volume is not complely s/complely/completely/ > writeable as there exists metadata which if overwritten will cause the > sparse lv to go INACTIVE which means pool-refresh will not find it. > Access to whatever lvm uses to manage data blocks is not provided by > any API I could find. > I wonder if lvm developers could point us to an alternative; maybe even lvreduce (shrink the allocated size) followed by lvresize (regrow it, but the new growth starts life empty) might behave semantically like a wipe. But yeah, we don't need to solve that today. > Signed-off-by: John Ferlan <jferlan@xxxxxxxxxx> > --- > src/storage/storage_backend_logical.c | 39 ++++++++++++++++++++++++++++++++++- > src/util/virstoragefile.h | 1 + > 2 files changed, 39 insertions(+), 1 deletion(-) > ACK -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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