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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> |
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| .. | ||
| ia32 | ||
| rpc | ||
| sys | ||
| util | ||
| assert.h | ||
| atomic.h | ||
| attr.h | ||
| devid.h | ||
| libdevinfo.h | ||
| libgen.h | ||
| libshare.h | ||
| limits.h | ||
| locale.h | ||
| Makefile.am | ||
| Makefile.in | ||
| note.h | ||
| priv.h | ||
| statcommon.h | ||
| stdio.h | ||
| stdlib.h | ||
| string.h | ||
| strings.h | ||
| stropts.h | ||
| synch.h | ||
| thread.h | ||
| tzfile.h | ||
| ucred.h | ||
| umem.h | ||
| unistd.h | ||
| zone.h | ||