netdev - [PATCH bpf-next 05/19] bpf: Remove migrate_{disable|enable} from bpf_task_storage

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Message-Id: <20250106081900.1665573-6-houtao@huaweicloud.com>
Date: Mon,  6 Jan 2025 16:18:46 +0800
From: Hou Tao <houtao@...weicloud.com>
To: bpf@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Martin KaFai Lau <martin.lau@...ux.dev>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Hao Luo <haoluo@...gle.com>,
	Yonghong Song <yonghong.song@...ux.dev>,
	Daniel Borkmann <daniel@...earbox.net>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Jiri Olsa <jolsa@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	houtao1@...wei.com,
	xukuohai@...wei.com
Subject: [PATCH bpf-next 05/19] bpf: Remove migrate_{disable|enable} from bpf_task_storage_lock helpers

From: Hou Tao <houtao1@...wei.com>

Three callers of bpf_task_storage_lock() are ->map_lookup_elem,
->map_update_elem, ->map_delete_elem from bpf syscall. BPF syscall for
these three operations of task storage has already disabled migration.
Another two callers are bpf_task_storage_get() and
bpf_task_storage_delete() helpers which will be used by BPF program.

Two callers of bpf_task_storage_trylock() are bpf_task_storage_get() and
bpf_task_storage_delete() helpers. The running contexts of these helpers
have already disabled migration.

Therefore, it is safe to remove migrate_{disable|enable} from task
storage lock helpers for these call sites. However,
bpf_task_storage_free() also invokes bpf_task_storage_lock() and its
running context doesn't disable migration, therefore, add the missed
migrate_{disable|enable} in bpf_task_storage_free().

Signed-off-by: Hou Tao <houtao1@...wei.com>
---
 kernel/bpf/bpf_task_storage.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index bf7fa15fdcc6..1109475953c0 100644
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -24,22 +24,20 @@ static DEFINE_PER_CPU(int, bpf_task_storage_busy);
 
 static void bpf_task_storage_lock(void)
 {
-	migrate_disable();
+	cant_migrate();
 	this_cpu_inc(bpf_task_storage_busy);
 }
 
 static void bpf_task_storage_unlock(void)
 {
 	this_cpu_dec(bpf_task_storage_busy);
-	migrate_enable();
 }
 
 static bool bpf_task_storage_trylock(void)
 {
-	migrate_disable();
+	cant_migrate();
 	if (unlikely(this_cpu_inc_return(bpf_task_storage_busy) != 1)) {
 		this_cpu_dec(bpf_task_storage_busy);
-		migrate_enable();
 		return false;
 	}
 	return true;
@@ -72,18 +70,19 @@ void bpf_task_storage_free(struct task_struct *task)
 {
 	struct bpf_local_storage *local_storage;
 
+	migrate_disable();
 	rcu_read_lock();
 
 	local_storage = rcu_dereference(task->bpf_storage);
-	if (!local_storage) {
-		rcu_read_unlock();
-		return;
-	}
+	if (!local_storage)
+		goto out;
 
 	bpf_task_storage_lock();
 	bpf_local_storage_destroy(local_storage);
 	bpf_task_storage_unlock();
+out:
 	rcu_read_unlock();
+	migrate_enable();
 }
 
 static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key)
-- 
2.29.2