ext3: make barrier options consistent with ext4
ext4 was updated to accept barrier/nobarrier mount options
in addition to the older barrier=0/1. The barrier story
is complex enough, we should help people by making the options
the same at least, even if the defaults are different.
This patch allows the barrier/nobarrier mount options for ext3,
while keeping nobarrier the default.
It also unconditionally displays barrier status in show_options,
and prints a message at mount time if barriers are not enabled,
just as ext4 does.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt
index 867c5b50..272f80d 100644
--- a/Documentation/filesystems/ext3.txt
+++ b/Documentation/filesystems/ext3.txt
@@ -59,8 +59,19 @@
Setting it to very large values will improve
performance.
-barrier=1 This enables/disables barriers. barrier=0 disables
- it, barrier=1 enables it.
+barrier=<0(*)|1> This enables/disables the use of write barriers in
+barrier the jbd code. barrier=0 disables, barrier=1 enables.
+nobarrier (*) This also requires an IO stack which can support
+ barriers, and if jbd gets an error on a barrier
+ write, it will disable again with a warning.
+ Write barriers enforce proper on-disk ordering
+ of journal commits, making volatile disk write caches
+ safe to use, at some performance penalty. If
+ your disks are battery-backed in one way or another,
+ disabling barriers may safely improve performance.
+ The mount options "barrier" and "nobarrier" can
+ also be used to enable or disable barriers, for
+ consistency with other ext3 mount options.
orlov (*) This enables the new Orlov block allocator. It is
enabled by default.
