ext4: make trim/discard optional (and off by default)
It is anticipated that when sb_issue_discard starts doing
real work on trim-capable devices, we may see issues. Make
this mount-time optional, and default it to off until we know
that things are working out OK.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 6d94e06..26904ff 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -353,6 +353,12 @@
system crashes before the delayed allocation
blocks are forced to disk.
+discard Controls whether ext4 should issue discard/TRIM
+nodiscard(*) commands to the underlying block device when
+ blocks are freed. This is useful for SSD devices
+ and sparse/thinly-provisioned LUNs, but it is off
+ by default until sufficient testing has been done.
+
Data Mode
=========
There are 3 different data modes: