Re: [patch] document ext3 a bit better

Pavel Machek
2009-01-06T09:20:18Z

On Mon 2009-01-05 09:57:13, Theodore Tso wrote:
> On Sun, Jan 04, 2009 at 11:34:33PM +0100, Pavel Machek wrote:
> > @@ -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". "ro, noload" can be used to prevent
> > + writes to the filesystem.
>
> I'd sugest "ro,noload" since the spaces screw up the mount options
> parsing both on the command-line and in /etc/fstab. So how about:
>
> Using the mount options "ro,noload" can be used....

Too many "using", but yes, fixed, thanks.

> > @@ -95,6 +102,8 @@ debug Extra debugging information is s
> > 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.
> > + (Note that default is overriden by superblock
> > + setting on most systems).
>
> The default is always specified by the superblock setting. So users
> will probably find it easier to understand if we remove the "(*)" and
> to add the explanatory comment:
>
> (These mount options override the errors behavior
> specified in the superblock, which can be configured
> using tune2fs)
>
> Pavel, thanks for working on improving the documentation; with these
> fixes,

Thanks!

---

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>

diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt
index 9dd2a3b..49c08bf 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 jou
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.

--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html