nilfs2: issue discard request after cleaning segments

This adds a function to send discard requests for given array of
segment numbers, and calls the function when garbage collection
succeeded.

Signed-off-by: Jiro SEKIBA <jir@unicus.jp>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

1 files changed, 3 insertions, 0 deletions

diff --git a/Documentation/filesystems/nilfs2.txt b/Documentation/filesystems/nilfs2.txt
index 839efd8a8a8c..cf6d0d85ca82 100644
--- a/Documentation/filesystems/nilfs2.txt
+++ b/Documentation/filesystems/nilfs2.txt
@@ -74,6 +74,9 @@ norecovery		Disable recovery of the filesystem on mount.
                         This disables every write access on the device for
                         read-only mounts or snapshots.  This option will fail
                         for r/w mounts on an unclean volume.
+discard                 Issue discard/TRIM commands to the underlying block
+                        device when blocks are freed.  This is useful for SSD
+                        devices and sparse/thinly-provisioned LUNs.
 
 NILFS2 usage
 ============