Re: [REGRESSION] ext4: oops in ext4_finish_bio() after enabling encryption on a mounted fs

[Eric Biggers <ebiggers@kernel.org>]

On Wed, Sep 23, 2026 at 09:28:54PM +0800, Baokun Li wrote:
> On 2026/9/23 20:40, Alberto Garcia wrote:
> > On Wed, Sep 23, 2026 at 08:12:03PM +0800, Baokun Li wrote:
> >>> 1) Enable encryption on an ext4 filesystem with tune2fs -O encrypt
> >> Is it valid to enable encrypt at mount time?
> > Good question, I always understood that it was allowed and tune2fs
> > certainly doesn't forbid it (compare with casefold):
> >
> > https://github.com/tytso/e2fsprogs/blob/v1.47.4/misc/tune2fs.c#L1599
> >
> > Berto
> 
> 
> If enabling encryption on a mounted ext4 fs is allowed,
> I think the current change is fine.
> 
> Ted, Eric - would either of you know the details here?

Yes, it is allowed.

The proposed patch looks good, even though the problem seems to be gone
on mainline already due to the removal of the code path that used the
non-large-folio-compatible function fscrypt_encrypt_pagecache_blocks().

There can be another patch that removes both that check and the
mount-time check, if they're truly no longer needed (I don't know of any
reason why they would be, but it needs to be properly tested).

- Eric