freebsd-nq/cmd
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
..
mount_zfs Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
sas_switch_id Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
zdb Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
zfs Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
zinject Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
zpios Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
zpool Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
zpool_id Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
zpool_layout Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
ztest Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
zvol_id Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00
Makefile.am Multipath device manageability improvements 2011-06-23 10:46:06 -07:00
Makefile.in Add support for DISCARD to ZVOLs. 2012-02-09 16:19:38 -08:00