eventfs: Remove "is_freed" union with rcu head

stable inclusion
from stable-v6.6.1
commit fa18a8a0539b02cc621938091691f0b73f0b1288
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8IKRU

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fa18a8a0539b02cc621938091691f0b73f0b1288

--------------------------------

commit f2f496370afcbc5227d7002da28c74b91fed12ff upstream

The eventfs_inode->is_freed was a union with the rcu_head with the
assumption that when it was on the srcu list the head would contain a
pointer which would make "is_freed" true. But that was a wrong assumption
as the rcu head is a single link list where the last element is NULL.

Instead, split the nr_entries integer so that "is_freed" is one bit and
the nr_entries is the next 31 bits. As there shouldn't be more than 10
(currently there's at most 5 to 7 depending on the config), this should
not be a problem.

Link: https://lkml.kernel.org/r/20231101172649.049758712@goodmis.org



Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ajay Kaher <akaher@vmware.com>
Fixes: 63940449 ("eventfs: Implement eventfs lookup, read, open functions")
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>