bpf: Remove migrate_{disable|enable} from bpf_cgrp_storage_lock helpers

Three callers of bpf_cgrp_storage_lock() are ->map_lookup_elem,
->map_update_elem, ->map_delete_elem from bpf syscall. BPF syscall for
these three operations of cgrp storage has already disabled migration.

Two call sites of bpf_cgrp_storage_trylock() are bpf_cgrp_storage_get(),
and bpf_cgrp_storage_delete() helpers. The running contexts of these
helpers have already disabled migration.

Therefore, it is safe to remove migrate_disable() for these callers.
However, bpf_cgrp_storage_free() also invokes bpf_cgrp_storage_lock()
and its running context doesn't disable migration. Therefore, also add
the missed migrate_{disabled|enable} in bpf_cgrp_storage_free().

Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-5-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: Hou Tao

kernel/bpf/bpf_cgrp_storage.c

@@ -15,22 +15,20 @@ static DEFINE_PER_CPU(int, bpf_cgrp_storage_busy);
 
 static void bpf_cgrp_storage_lock(void)
 {
-	migrate_disable();
+	cant_migrate();
 	this_cpu_inc(bpf_cgrp_storage_busy);
 }
 
 static void bpf_cgrp_storage_unlock(void)
 {
 	this_cpu_dec(bpf_cgrp_storage_busy);
-	migrate_enable();
 }
 
 static bool bpf_cgrp_storage_trylock(void)
 {
-	migrate_disable();
+	cant_migrate();
 	if (unlikely(this_cpu_inc_return(bpf_cgrp_storage_busy) != 1)) {
 		this_cpu_dec(bpf_cgrp_storage_busy);
-		migrate_enable();
 		return false;
 	}
 	return true;
@@ -47,17 +45,18 @@ void bpf_cgrp_storage_free(struct cgroup *cgroup)
 {
 	struct bpf_local_storage *local_storage;
 
+	migrate_disable();
 	rcu_read_lock();
 	local_storage = rcu_dereference(cgroup->bpf_cgrp_storage);
-	if (!local_storage) {
-		rcu_read_unlock();
-		return;
-	}
+	if (!local_storage)
+		goto out;
 
 	bpf_cgrp_storage_lock();
 	bpf_local_storage_destroy(local_storage);
 	bpf_cgrp_storage_unlock();
+out:
 	rcu_read_unlock();
+	migrate_enable();
 }
 
 static struct bpf_local_storage_data *