Re: Stacking filesystem deadlocks [was Re: Fanotify (hsm or erofs) / fuse / nbd / ... + write(mmap) deadlock vector followup]

[Gao Xiang <hsiangkao@linux.alibaba.com>]

On 2026/6/17 21:37, Christian Brauner wrote:
> On Thu, Jun 11, 2026 at 05:25:56PM +0200, Amir Goldstein wrote:
>> On Thu, Jun 11, 2026 at 1:32 PM Jan Kara <jack@suse.cz> wrote:

...

>>
>> My crystal ball tells me we are probably not going to do that :-/
>> But if we did, it would have been nice to validate that LOOP_CHANGE_FD
>> does not set the backing file of loopA to a file on fsB ;)
> 
> LOOP_CHANGE_FD should be removed. I proposed that years ago because it's
> problematic in other ways. Everyone agreed as it was effectively unused
> I just never bothered pushing it through. So let's not worry about that
> let's kill it instead. Here's the patch from 2023:
> 
>  From 46db77d781d329b7fc7b3245dd295a69026f6ec0 Mon Sep 17 00:00:00 2001
> From: Christian Brauner <brauner@kernel.org>
> Date: Mon, 6 Nov 2023 16:29:32 +0100
> Subject: [PATCH] loop: remove support for swapping loop fds
> 
> We did not find any users of LOOP_CHANGE_FD.
> 
> Signed-off-by: Christian Brauner <brauner@kernel.org>

I am glad if it could be dropped so at least I will not
worry about missing features if fs shutdown is
implemented in erofs.

Thanks,
Gao Xiang