From 23f6b02405343103791c6a9533d73716cdf0c672 Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Wed, 18 Dec 2019 12:12:10 +0100
Subject: [PATCH] ext4: clarify impact of 'commit' mount option
The description of 'commit' mount option dates back to ext3 times.
Update the description to match current meaning for ext4.
Reported-by: Paul Richards <paul.richards@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191218111210.14161-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
Documentation/admin-guide/ext4.rst | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/Documentation/admin-guide/ext4.rst b/Documentation/admin-guide/ext4.rst
index 059ddcbe769d9..9bc93f0ce0c90 100644
--- a/Documentation/admin-guide/ext4.rst
+++ b/Documentation/admin-guide/ext4.rst
@@ -181,14 +181,17 @@ When mounting an ext4 filesystem, the following option are accepted:
system after its metadata has been committed to the journal.
commit=nrsec (*)
- Ext4 can be told to sync all its data and metadata every 'nrsec'
- seconds. The default value is 5 seconds. This means that if you lose
- your power, you will lose as much as the latest 5 seconds of work (your
- filesystem will not be damaged though, thanks to the journaling). This
- default value (or any low value) will hurt performance, but it's good
- for data-safety. Setting it to 0 will have the same effect as leaving
- it at the default (5 seconds). Setting it to very large values will
- improve performance.
+ This setting limits the maximum age of the running transaction to
+ 'nrsec' seconds. The default value is 5 seconds. This means that if
+ you lose your power, you will lose as much as the latest 5 seconds of
+ metadata changes (your filesystem will not be damaged though, thanks
+ to the journaling). This default value (or any low value) will hurt
+ performance, but it's good for data-safety. Setting it to 0 will have
+ the same effect as leaving it at the default (5 seconds). Setting it
+ to very large values will improve performance. Note that due to
+ delayed allocation even older data can be lost on power failure since
+ writeback of those data begins only after time set in
+ /proc/sys/vm/dirty_expire_centisecs.
barrier=<0|1(*)>, barrier(*), nobarrier
This enables/disables the use of write barriers in the jbd code.
--
2.30.2