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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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| .. | ||
| asm-generic | ||
| asm-i386 | ||
| asm-x86_64 | ||
| include | ||
| getexecname.c | ||
| gethrestime.c | ||
| gethrtime.c | ||
| getmntany.c | ||
| list.c | ||
| Makefile.am | ||
| Makefile.in | ||
| mkdirp.c | ||
| strlcat.c | ||
| strlcpy.c | ||
| strnlen.c | ||
| timestamp.c | ||
| xdr.c | ||
| zone.c | ||