Re: [PATCH v2] super: make iterate_supers_type() deletion-safe

[Christian Brauner]

On Wed, 09 Sep 2026 21:30:34 +0200, Karl Mehltretter wrote:
> iterate_supers_type() drops sb_lock while invoking the callback and keeps
> only a passive reference to the current superblock. That reference keeps
> the object allocated, but does not keep its s_instances node linked.
> 
> After the iterator releases s_umount, final teardown can unlink the current
> s_instances node. The iterator then advances through a reinitialized node.
> With the current hlist it stops without visiting the remaining superblocks.
> The unlink moved from generic_shutdown_super() to kill_super_notify(), but
> the cursor lifetime has been unsafe since the helper was introduced.
> 
> [...]

I'm moving this into vfs-7.4.misc for now but will bump it to vfs.fixes once
I'm confident this is safe.

---

Applied to the vfs-7.4.misc branch of the vfs/vfs.git tree.
Patches in the vfs-7.4.misc branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-7.4.misc

[1/1] super: make iterate_supers_type() deletion-safe
      https://git.kernel.org/vfs/vfs/c/d1ac530407a3