nilfs2: add nodiscard mount option

Nilfs has "discard" mount option which issues discard/TRIM commands to
underlying block device, but it lacks a complementary option and has
no way to disable the feature through remount.

This adds "nodiscard" option to resolve this imbalance.

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

1 files changed, 4 insertions, 3 deletions

diff --git a/Documentation/filesystems/nilfs2.txt b/Documentation/filesystems/nilfs2.txt
index 54f61c0ff442..d5c0cef38a71 100644
--- a/Documentation/filesystems/nilfs2.txt
+++ b/Documentation/filesystems/nilfs2.txt
@@ -77,9 +77,10 @@ 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.
+discard                 This enables/disables the use of discard/TRIM commands.
+nodiscard(*)            The discard/TRIM commands are sent to the underlying
+                        block device when blocks are freed.  This is useful
+                        for SSD devices and sparse/thinly-provisioned LUNs.
 
 NILFS2 usage
 ============