super: take lock after last reference count

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__put_super() required the caller to hold sb_lock, so put_super()
wrapped it. The per-device superblock table introduced later drops its
passive references from contexts that do not hold sb_lock, so make
put_super() self-locking: drop the count first and take sb_lock only for
the final list_del.

With the count now dropped outside sb_lock a superblock can briefly sit
on @super_blocks with s_passive == 0 before it is unlinked, so the list
walkers (__iterate_supers(), iterate_supers_type(), user_get_super())
switch to refcount_inc_not_zero() and skip it.

Link: https://patch.msgid.link/20260616-work-super-bdev_holder_global-v2-3-7df6b864028e@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

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Christian Brauner 2026-06-16 16:08:19 +02:00

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fs/super.c

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