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

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.