[RFC v3 2/5] bpf: Explicitly align bpf_res_spin_lock

[Finn Thain]

Align bpf_res_spin_lock to avoid a BUILD_BUG_ON() when the alignment
changes, as it will do on m68k when, in a subsequent patch, the minimum
alignment of the atomic_t member of struct rqspinlock gets increased.
Drop the BUILD_BUG_ON() as it is now redundant.

Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx>
Cc: Eduard Zingerman <eddyz87@xxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Yonghong Song <yonghong.song@xxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: KP Singh <kpsingh@xxxxxxxxxx>
Cc: Stanislav Fomichev <sdf@xxxxxxxxxxx>
Cc: Hao Luo <haoluo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
---
 include/asm-generic/rqspinlock.h | 2 +-
 kernel/bpf/rqspinlock.c          | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/asm-generic/rqspinlock.h b/include/asm-generic/rqspinlock.h
index 6d4244d643df..eac2dcd31b83 100644
--- a/include/asm-generic/rqspinlock.h
+++ b/include/asm-generic/rqspinlock.h
@@ -28,7 +28,7 @@ struct rqspinlock {
  */
 struct bpf_res_spin_lock {
 	u32 val;
-};
+} __aligned(__alignof__(struct rqspinlock));
 
 struct qspinlock;
 #ifdef CONFIG_QUEUED_SPINLOCKS
diff --git a/kernel/bpf/rqspinlock.c b/kernel/bpf/rqspinlock.c
index 338305c8852c..a88a0e9749d7 100644
--- a/kernel/bpf/rqspinlock.c
+++ b/kernel/bpf/rqspinlock.c
@@ -671,7 +671,6 @@ __bpf_kfunc int bpf_res_spin_lock(struct bpf_res_spin_lock *lock)
 	int ret;
 
 	BUILD_BUG_ON(sizeof(rqspinlock_t) != sizeof(struct bpf_res_spin_lock));
-	BUILD_BUG_ON(__alignof__(rqspinlock_t) != __alignof__(struct bpf_res_spin_lock));
 
 	preempt_disable();
 	ret = res_spin_lock((rqspinlock_t *)lock);
-- 
2.49.1