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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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| 1th-16rc-4rs-1cs-4off.sh | ||
| 1x256th-65536rc-4rs-1cs-4off.sh | ||
| 4th-1024rc-4rs-1cs-4off.sh | ||
| 16th-8192rc-4rs-1cs-4off.sh | ||
| 256th-65536rc-4rs-1cs-4off.sh | ||
| large-thread-survey.sh | ||
| large.sh | ||
| lustre.sh | ||
| Makefile.am | ||
| Makefile.in | ||
| medium.sh | ||
| small.sh | ||
| tiny.sh | ||