For 8-bit and 16-bit sign-extention mov instructions, it can use the
native instructions ext.w.b and ext.w.h directly, no need to use the
temporary t1 register, just remove the redundant operations.

Here are the test results:

  # modprobe test_bpf test_range=81,84
  # dmesg -t | tail -5
  test_bpf: #81 ALU_MOVSX | BPF_B jited:1 5 PASS
  test_bpf: #82 ALU_MOVSX | BPF_H jited:1 5 PASS
  test_bpf: #83 ALU64_MOVSX | BPF_B jited:1 5 PASS
  test_bpf: #84 ALU64_MOVSX | BPF_H jited:1 5 PASS
  test_bpf: Summary: 4 PASSED, 0 FAILED, [4/4 JIT'ed]

Acked-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Currently, get_non_dying_memcg_start() and get_non_dying_memcg_end() both
evaluate cgroup_subsys_on_dfl(memory_cgrp_subsys) independently to
determine whether to acquire or release the RCU read lock.

However, the result of cgroup_subsys_on_dfl() can change dynamically at
runtime due to cgroup hierarchy rebinding (e.g., when the memory
controller is moved between cgroup v1 and v2 hierarchies).  This can cause
the following warning:

 =====================================
 WARNING: bad unlock balance detected!
 7.0.0-next-20260420+ Rust-for-Linux#83 Tainted: G        W
 -------------------------------------
 memcg-repro/270 is trying to release lock (rcu_read_lock) at:
 [<ffffffff815f57f7>] rcu_read_unlock+0x17/0x60
 but there are no more locks to release!

 other info that might help us debug this:
 1 lock held by memcg-repro/270:
  #0: ffff888102fa2088 (vm_lock){++++}-{0:0}, at: do_user_addr_fault+0x285/0x880

 stack backtrace:
 CPU: 0 UID: 0 PID: 270 Comm: memcg-repro Tainted: G        W           7.0.0-next-20260420+ #
 Tainted: [W]=WARN
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
 Call Trace:
  <TASK>
  ? rcu_read_unlock+0x17/0x60
  dump_stack_lvl+0x77/0xb0
  print_unlock_imbalance_bug+0xe0/0xf0
  ? rcu_read_unlock+0x17/0x60
  lock_release+0x21d/0x2a0
  rcu_read_unlock+0x1c/0x60
  do_pte_missing+0x233/0xb40
  __handle_mm_fault+0x80e/0xcd0
  handle_mm_fault+0x146/0x310
  do_user_addr_fault+0x303/0x880
  exc_page_fault+0x9b/0x270
  asm_exc_page_fault+0x26/0x30
 RIP: 0033:0x5590e4eb41ea
 Code: 61 cc 66 0f 6f e0 66 0f 61 c2 66 0f db cd 66 0f 69 e2 66 0f 6f d0 66 0f 69 d4 66 0f 61 0
 RSP: 002b:00007ffcad25f030 EFLAGS: 00010202
 RAX: 00005590e4eb8010 RBX: 00007ffcad260f7d RCX: 00007f73c474d44d
 RDX: 00005590e4eb80a0 RSI: 00005590e4eb503c RDI: 000000000000000f
 RBP: 00005590e4eb70a0 R08: 0000000000000000 R09: 00007f73c483a680
 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
 R13: 00007ffcad25f180 R14: 00005590e4eb6dd8 R15: 00007f73c4869020
  </TASK>
 ------------[ cut here ]------------

Fix this by explicitly tracking the RCU lock state, ensuring that
rcu_read_unlock() in get_non_dying_memcg_end() is strictly paired with the
lock acquisition, regardless of any runtime rebinding events.

Link: https://lore.kernel.org/20260429073105.44472-1-qi.zheng@linux.dev
Fixes: 8285917 ("mm: memcontrol: prepare for reparenting non-hierarchical stats")
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>