[PATCH] ext4: Register ext[23] support only after successful ext4 registration

[PATCH] ext4: Register ext[23] support only after successful ext4 registration

[Marc Aurèle La France]

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Register ext4 as a "replacement" for ext2 and ext3 only after ext4 itself has
been successfully registered.  As a side effect, this allows
unregister_as_ext[23]() to be inlined.

This change is not eligible for stable@.

Please Reply-To-All.

Thanks and have a great day.

Marc.

Signed-off-by: Marc Aurèle La France <tsi@tuyoix.net>

diff -aNpRruz -X /etc/diff.excludes linux-5.17.1/fs/ext4/super.c devel-5.17.1/fs/ext4/super.c
--- linux-5.17.1/fs/ext4/super.c	2022-03-28 02:03:22.000000000 -0600
+++ devel-5.17.1/fs/ext4/super.c	2022-03-28 07:14:10.799008309 -0600
@@ -7123,16 +7123,14 @@ static int __init ext4_init_fs(void)
 	if (err)
 		goto out05;

-	register_as_ext3();
-	register_as_ext2();
 	err = register_filesystem(&ext4_fs_type);
 	if (err)
 		goto out;

+	register_as_ext3();
+	register_as_ext2();
 	return 0;
 out:
-	unregister_as_ext2();
-	unregister_as_ext3();
 	ext4_fc_destroy_dentry_cache();
 out05:
 	destroy_inodecache();

Re: [PATCH] ext4: Register ext[23] support only after successful ext4 registration

[Theodore Ts'o]

On Wed, Aug 10, 2022 at 02:20:45PM -0600, Marc Aurèle La France wrote:
> Register ext4 as a "replacement" for ext2 and ext3 only after ext4 itself has
> been successfully registered.  As a side effect, this allows
> unregister_as_ext[23]() to be inlined.

The corrent ordering is deliberate; it allows file systems that have
ext2 and ext3 only file system features will be reported as using ext2
and ext3 in /proc/mounts.  This doesn't matter quite as much, but it
could potentially break userspace if a legacy file system that only
has ext2 file system features is mounted and reported as ext4.

So sorry, I can't take this change.

					- Ted

Re: [PATCH] ext4: Register ext[23] support only after successful ext4 registration

[Marc Aurèle La France]

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On Thu, 29 Sep 2022, Theodore Ts'o wrote:
> On Wed, Aug 10, 2022 at 02:20:45PM -0600, Marc Aurèle La France wrote:
>> Register ext4 as a "replacement" for ext2 and ext3 only after ext4 itself has
>> been successfully registered.  As a side effect, this allows
>> unregister_as_ext[23]() to be inlined.

> The corrent ordering is deliberate; it allows file systems that have
> ext2 and ext3 only file system features will be reported as using ext2
> and ext3 in /proc/mounts.  This doesn't matter quite as much, but it
> could potentially break userspace if a legacy file system that only
> has ext2 file system features is mounted and reported as ext4.

> So sorry, I can't take this change.

Fair enough.  Thanks for responding.

Marc.