Bug 770172

The info in the man page is incorrect. The correct is "check=none" *or* "nocheck" according to the kernel docs. 
 
Anyway, the option does not make sense. It's default behaviour and non-default behaviour is unsupported. I'll update the man page. Thanks for your report.

> I bumped into that because in the past mount, at least for various ext? file
> systems, accepted '-o nocheck,...'.  This does not work anymore and breaks some
> existing scripts after F14->F16 changeover.  Oh, well....

The Fedora kernel uses ext4 driver to mount ext2 and ext3 filesystems. Unfortunately, it seems that this solution is not 100% backwardly compatible with the original ext2 and ext3 drivers.... reassigning to kernel guys.

Note, the mount.8 man pages fixed by util-linux upstream commit c6238085a12baa45d7270e73a181c20b81586bee.

(In reply to comment #1)
> The info in the man page is incorrect. The correct is "check=none" *or*
> "nocheck" according to the kernel docs. 
> 
> Anyway, the option does not make sense. It's default behaviour and non-default
> behaviour is unsupported. I'll update the man page. Thanks for your report.

As Karel said, the non-default behavior (check=normal, check=strict) is unsupported.  The check= and nocheck options are basically just silently eaten on ext2/ext3.

> > I bumped into that because in the past mount, at least for various ext? file
> > systems, accepted '-o nocheck,...'.  This does not work anymore and breaks some
> > existing scripts after F14->F16 changeover.  Oh, well....
> 
> The Fedora kernel uses ext4 driver to mount ext2 and ext3 filesystems.
> Unfortunately, it seems that this solution is not 100% backwardly compatible
> with the original ext2 and ext3 drivers.... reassigning to kernel guys.

Eric, does this patch seem reasonable for upstream (ignore bugzilla line wrapping)?

---

From ea75f7357e3a881bd1bd0db5e483fc6a8681567b Mon Sep 17 00:00:00 2001
From: Josh Boyer <jwboyer>
Date: Tue, 10 Jan 2012 09:39:02 -0500
Subject: [PATCH] ext4: Support "check=none" "nocheck" mount options

The ext2/ext3 filesystems supported "check=none" and "nocheck" as mount options
even though that was already the default behavior and it essentially did
nothing.  When using ext4 to mount ext2/ext3 filesystems, that mount option
causes the mount to fail.  That isn't as backward compatible as it could be,
so add support to ext4 to accept the option.

Signed-off-by: Josh Boyer <jwboyer>
---
 fs/ext4/super.c |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 3e1329e..5ff09e7 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1333,7 +1333,7 @@ enum {
 	Opt_nomblk_io_submit, Opt_block_validity, Opt_noblock_validity,
 	Opt_inode_readahead_blks, Opt_journal_ioprio,
 	Opt_dioread_nolock, Opt_dioread_lock,
-	Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
+	Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable, Opt_nocheck,
 };
 
 static const match_table_t tokens = {
@@ -1409,6 +1409,8 @@ static const match_table_t tokens = {
 	{Opt_init_itable, "init_itable=%u"},
 	{Opt_init_itable, "init_itable"},
 	{Opt_noinit_itable, "noinit_itable"},
+	{Opt_nocheck, "check=none"},
+	{Opt_nocheck, "nocheck"},
 	{Opt_err, NULL},
 };
 
@@ -1905,6 +1907,9 @@ set_qf_format:
 		case Opt_noinit_itable:
 			clear_opt(sb, INIT_INODE_TABLE);
 			break;
+		case Opt_nocheck:
+			/* ext2/ext3 used to "support" this option.  Silently eat it */
+			break;
 		default:
 			ext4_msg(sb, KERN_ERR,
 			       "Unrecognized mount option \"%s\" "
-- 
1.7.7.5

Josh, that seems ok.  Looks like _CHECK is a complete do-nothing?  It's only ever "cleared" (having been impossible to set) even in ext2?

Yay, more cruft to carry along!  But that looks like the right plan.

Thanks,
-Eric

I tested this locally with a loopback filesystem.  Before the patch:

[jwboyer@vader ~]$ sudo mount -o loop ./ext2.img /mnt/
[jwboyer@vader ~]$ ls /mnt/
lost+found
[jwboyer@vader ~]$ sudo umount /mnt
[jwboyer@vader ~]$ sudo mount -o loop,nocheck ./ext2.img /mnt/
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

[jwboyer@vader ~]$ 

After:

[jwboyer@vader ~]$ sudo mount -o loop,nocheck ./ext2.img /mnt
[jwboyer@vader ~]$ ls /mnt
lost+found
[jwboyer@vader ~]$ sudo umount /mnt
[jwboyer@vader ~]$ sudo mount -o loop,check=none ./ext2.img /mnt
[jwboyer@vader ~]$ sudo umount /mnt

Patch sent upstream:

http://patchwork.ozlabs.org/patch/135270/

I committed the patch to Rawhide and f16.  F15 isn't impacted because we still build the ext2 module there instead of use ext4.

kernel-3.1.9-1.fc16 has been submitted as an update for Fedora 16.
https://admin.fedoraproject.org/updates/kernel-3.1.9-1.fc16

kernel-3.1.9-1.fc16 has been pushed to the Fedora 16 stable repository.  If problems still persist, please make note of it in this bug report.