Etienne Dechamps 30930fba21 Add support for DISCARD to ZVOLs. ... DISCARD (REQ_DISCARD, BLKDISCARD) is useful for thin provisioning. It allows ZVOL clients to discard (unmap, trim) block ranges from a ZVOL, thus optimizing disk space usage by allowing a ZVOL to shrink instead of just grow. We can't use zfs_space() or zfs_freesp() here, since these functions only work on regular files, not volumes. Fortunately we can use the low-level function dmu_free_long_range() which does exactly what we want. Currently the discard operation is not added to the log. That's not a big deal since losing discard requests cannot result in data corruption. It would however result in disk space usage higher than it should be. Thus adding log support to zvol_discard() is probably a good idea for a future improvement. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>		2012-02-09 16:19:38 -08:00
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dragon.ddn.conf	Add [-m map] option to zpool_layout	2010-09-17 11:02:19 -07:00
dragon.llnl.conf	Add [-m map] option to zpool_layout	2010-09-17 11:02:19 -07:00
Makefile.am	Add [-m map] option to zpool_layout	2010-09-17 11:02:19 -07:00
Makefile.in	Add support for DISCARD to ZVOLs.	2012-02-09 16:19:38 -08:00