Hi,

The same happened to me a while ago. It's because the filesystem is ext3 and
you mount it as ext2. Yes, they are compatible, you can mount an ext3
partition as ext2 but ONLY if the partition was _cleanly_ unmounted before.
My suggestion is: either do a fsch.ext3 on your new filesystem from within
the host OS, or compile your target kernel with ext3 support and mount the
partition as ext3.

Regards,
Alex

-----Original Message-----
From: Yedidyah Bar-David [mailto:[EMAIL PROTECTED] 
Sent: Friday, October 01, 2004 10:56
To: Diego Iastrubni
Cc: Linux List
Subject: Re: ext2[3] options - sparse_super

On Fri, Oct 01, 2004 at 03:25:03AM +0200, Diego Iastrubni wrote:
> The target system is PCLinusOS (Mandrake). Some 2.4.2(something) kernel.
> The host is Debian (testing).
> The partition is not marked as bootable (who cares about it?)
> 
> The kernel loads, and when it shuold remount the rootfs it dies with
error:

You probably mean "mounting" - the kernel _remounts_ a bit later during
the boot process (if at all) by a script, not something which should
panic it.

> "EXT2-fs: ide(3,3): couldn't mount because of unsupported optional
features 
> (4).
> Kernel panic: VFS: Unable to mount root fs on 03:03."
> 
> The file system was made by running 
> "mkfs.ext3 /dev/hda3"
> 
> Didi,
> Not sure what my problem is, just shooting in blindly in the air.

I was under the impression that you know the missing feature is
sparse_super, only wanting to find out more about it.

>  
> If anyone knows the relevant code of the kernel I could RTFS and learn :)

Well, a quick grep finds:

fs/ext3/super.c:
        if ((i = EXT3_HAS_INCOMPAT_FEATURE(sb,
~EXT3_FEATURE_INCOMPAT_SUPP))) {
                printk(KERN_ERR "EXT3-fs: %s: couldn't mount because of "
                       "unsupported optional features (%x).\n",
                       bdevname(dev), i);
                goto failed_mount;
        }
And
include/linux/ext3_fs.h:
#define EXT3_FEATURE_INCOMPAT_RECOVER           0x0004 /* Needs recovery */
#define EXT3_FEATURE_INCOMPAT_SUPP      (EXT3_FEATURE_INCOMPAT_FILETYPE| \
                                         EXT3_FEATURE_INCOMPAT_RECOVER| \
                                         EXT3_FEATURE_INCOMPAT_META_BG)

grepping for EXT3_FEATURE_INCOMPAT_RECOVER (which seems to me to be the
root cause) does find it some more times, but I can't say that from a
quick glance at the code I understand what it does.
The release notes file for e2fsprogs does mention some 'recovery flag'.
Maybe google for EXT3_FEATURE_INCOMPAT_RECOVER?
-- 
Didi


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