Re: simplify ext4_sb_read_encoding regression

["Theodore Ts'o" <tytso@mit.edu>]

On Sat, May 28, 2022 at 06:53:59PM -0400, Stephen E. Baker wrote:
> Hello,
> 
> I have a Samsung Chromebook Plus (rk3399-gru-kevin) which boots linux off
> an external ssd plugged into USB. The root filesystem is ext4 with unicode
> support, case folding is enabled only on some directories in my home
> directory.
> 
> Since 5.17 the system has been unbootable.

Can you boot using an older kernel and send me (a) the output of
dumpe2fs -h of your root file system, and (b) the output of running
dmesg immediately after the system is booted?

If you can capture the console output when trying to boot 5.17, that
would be helpful.  You may need to disable the graphical boot screen
depending on what distribution or how the bootloader is configured.
If you could to take a picture of the screen when it stops/hangs, that
would be helpful.

I don't see anything wrong with the commit, and I've tested booting
the root file system with casefold enabled, and it works just fine.
What I did was take the root_fs.img from kvm-xfstests[1], and did the
following:

% qemu-img convert -O raw test-appliance/root_fs.img /tmp/root_fs.raw
% tune2fs -O casefold /tmp/root_fs.raw
% qemu-img convert -f raw -O qcow2 /tmp/root_fs.raw /tmp/root_fs.img
% kvm-xfstests -I /tmp/root_fs.img shell

and 5.17 booted without any problems.

[1] https://github.com/tytso/xfstests-bld/blob/master/Documentation/kvm-quickstart.md

Once in the kvm environment:

root@kvm-xfstests:~# uname -a
Linux kvm-xfstests 5.17.0-xfstests #644 SMP PREEMPT Sat May 28 21:06:37 EDT 2022 x86_64 GNU/Linux

root@kvm-xfstests:~# dmesg | grep EXT4-fs
[    0.690089] EXT4-fs (vda): Using encoding defined by superblock: utf8-12.1.0 with flags 0x0
[    0.690161] EXT4-fs (vda): Using encoding defined by superblock: utf8-12.1.0 with flags 0x0
[    0.690592] EXT4-fs (vda): mounted filesystem without journal. Quota mode: none.
[    0.846407] EXT4-fs (vda): re-mounted. Quota mode: none.
[    1.144539] EXT4-fs (vdg): mounted filesystem with ordered data mode. Quota mode: no

root@kvm-xfstests:~# dumpe2fs -h /dev/vda 2>/dev/null | grep -i features
Filesystem features:      ext_attr resize_inode dir_index filetype extent 64bit flex_bg casefold sparse_super large_file huge_file dir_nlink extra_isize metadata_csum

root@kvm-xfstests:~# dumpe2fs -h /dev/vda 2>/dev/null | grep -i encoding
Character encoding:       utf8-12.1

I'm not sure what is going on with your system, but I can't reproduce
it on my end.

Regards,

						- Ted