trivial: document ext3 semantics of 'ro' option a bit better

ext3 has quite unexpected semantics or "ro" and defaults are
not what they are documented to be, due to mkfs override.

Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 12 insertions, 2 deletions

diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt
index e5f3833a6ef..570f9bd9be2 100644
--- a/Documentation/filesystems/ext3.txt
+++ b/Documentation/filesystems/ext3.txt
@@ -14,6 +14,11 @@ Options
 When mounting an ext3 filesystem, the following option are accepted:
 (*) == default
 
+ro                      Mount filesystem read only. Note that ext3 will replay
+                        the journal (and thus write to the partition) even when
+                        mounted "read only". Mount options "ro,noload" can be
+                        used to prevent writes to the filesystem.
+
 journal=update          Update the ext3 file system's journal to the current
                         format.
 
@@ -27,7 +32,9 @@ journal_dev=devnum	When the external journal device's major/minor numbers
                         identified through its new major/minor numbers encoded
                         in devnum.
 
-noload                  Don't load the journal on mounting.
+noload                  Don't load the journal on mounting. Note that this forces
+                        mount of inconsistent filesystem, which can lead to
+                        various problems.
 
 data=journal            All data are committed into the journal prior to being
                         written into the main file system.
@@ -92,9 +99,12 @@ nocheck
 
 debug                   Extra debugging information is sent to syslog.
 
-errors=remount-ro(*)    Remount the filesystem read-only on an error.
+errors=remount-ro       Remount the filesystem read-only on an error.
 errors=continue         Keep going on a filesystem error.
 errors=panic            Panic and halt the machine if an error occurs.
+                        (These mount options override the errors behavior
+                        specified in the superblock, which can be
+                        configured using tune2fs.)
 
 data_err=ignore(*)      Just print an error message if an error occurs
                         in a file data buffer in ordered mode.