diff options
| author | Etienne Dechamps <[email protected]> | 2011-09-02 15:23:12 +0200 |
|---|---|---|
| committer | Brian Behlendorf <[email protected]> | 2012-02-09 16:19:38 -0800 |
| commit | 30930fba219642cb1dadf1c8ef60ff799e3dc424 (patch) | |
| tree | 093f2c5c254768e859f8307d77d393e9668b5e1f /zfs_config.h.in | |
| parent | cb2d19010d8fbcf6c22585cd8763fad3ba7db724 (diff) | |
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 <[email protected]>
Diffstat (limited to 'zfs_config.h.in')
| -rw-r--r-- | zfs_config.h.in | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/zfs_config.h.in b/zfs_config.h.in index c91735a8e..887f0f7c9 100644 --- a/zfs_config.h.in +++ b/zfs_config.h.in @@ -51,6 +51,9 @@ /* blk_fetch_request() is available */ #undef HAVE_BLK_FETCH_REQUEST +/* blk_queue_discard() is available */ +#undef HAVE_BLK_QUEUE_DISCARD + /* blk_queue_flush() is available */ #undef HAVE_BLK_QUEUE_FLUSH |