linux-kernel - Re: [patch] document ext3 a bit better

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Message-ID: <20090106092156.GA13737@elf.ucw.cz>
Date:	Tue, 6 Jan 2009 10:21:56 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	Theodore Tso <tytso@....edu>,
	kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, mtk.manpages@...il.com,
	rdunlap@...otime.net, linux-doc@...r.kernel.org,
	Trivial patch monkey <trivial@...nel.org>
Subject: Re: [patch] document ext3 a bit better

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@...e.cz>
Signed-off-by: "Theodore Ts'o" <tytso@....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
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