netdev - [PATCH bpf-next 18/19] bpf: Remove migrate_{disable|enable} from bpf_local_storage

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Message-Id: <20250106081900.1665573-19-houtao@huaweicloud.com>
Date: Mon,  6 Jan 2025 16:18:59 +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 18/19] bpf: Remove migrate_{disable|enable} from bpf_local_storage_free()

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

bpf_local_storage_free() has three callers:

1) bpf_local_storage_alloc()
Its caller must have disabled migration.

2) bpf_local_storage_destroy()
Its four callers (bpf_{cgrp|inode|task|sk}_storage_free()) have already
invoked migrate_disable() before invoking bpf_local_storage_destroy().

3) bpf_selem_unlink()
Its callers include: cgrp/inode/task/sk storage ->map_delete_elem
callbacks, bpf_{cgrp|inode|task|sk}_storage_delete() helpers and
bpf_local_storage_map_free(). All of these callers have already disabled
migration before invoking bpf_selem_unlink().

Therefore, it is OK to remove migrate_{disable|enable} pair from
bpf_local_storage_free(). Also add a cant_migrate() check in
bpf_local_storage_free() to ensure the guarantee isn't broken.

Signed-off-by: Hou Tao <houtao1@...wei.com>
---
 kernel/bpf/bpf_local_storage.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 0970766278f7..d67ba116aee8 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -163,6 +163,8 @@ static void bpf_local_storage_free(struct bpf_local_storage *local_storage,
 	if (!local_storage)
 		return;
 
+	cant_migrate();
+
 	if (!bpf_ma) {
 		__bpf_local_storage_free(local_storage, reuse_now);
 		return;
@@ -174,17 +176,14 @@ static void bpf_local_storage_free(struct bpf_local_storage *local_storage,
 		return;
 	}
 
-	if (smap) {
-		migrate_disable();
+	if (smap)
 		bpf_mem_cache_free(&smap->storage_ma, local_storage);
-		migrate_enable();
-	} else {
+	else
 		/* smap could be NULL if the selem that triggered
 		 * this 'local_storage' creation had been long gone.
 		 * In this case, directly do call_rcu().
 		 */
 		call_rcu(&local_storage->rcu, bpf_local_storage_free_rcu);
-	}
 }
 
 /* rcu tasks trace callback for bpf_ma == false */
-- 
2.29.2