diff mbox series

[bpf-next,19/19] bpf: Remove migrate_{disable|enable} from bpf_selem_free()

Message ID 20250106081900.1665573-20-houtao@huaweicloud.com (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series [bpf-next,01/19] bpf: Remove migrate_{disable|enable} from LPM trie | expand

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Commit Message

Hou Tao Jan. 6, 2025, 8:19 a.m. UTC 
From: Hou Tao <houtao1@huawei.com>

bpf_selem_free() has the following three callers:

(1) bpf_local_storage_update
It will be invoked through ->map_update_elem syscall or helpers for
storage map. Migration has already been disabled in these running
contexts.

(2) bpf_sk_storage_clone
It has already disabled migration before invoking bpf_selem_free().

(3) bpf_selem_free_list
bpf_selem_free_list() has three callers: bpf_selem_unlink_storage(),
bpf_local_storage_update() and bpf_local_storage_destroy().

The callers of bpf_selem_unlink_storage() includes: storage map
->map_delete_elem syscall, storage map delete helpers and
bpf_local_storage_map_free(). These contexts have already disabled
migration when invoking bpf_selem_unlink() which invokes
bpf_selem_unlink_storage() and bpf_selem_free_list() correspondingly.

bpf_local_storage_update() has been analyzed as the first caller above.
bpf_local_storage_destroy() is invoked when freeing the local storage
for the kernel object. Now cgroup, task, inode and sock storage have
already disabled migration before invoking bpf_local_storage_destroy().

After the analyses above, it is safe to remove migrate_{disable|enable}
from bpf_selem_free(). Also add a cant_migrate() check in
bpf_selem_free().

Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 kernel/bpf/bpf_local_storage.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index d67ba116aee8..f196093db0a0 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -235,6 +235,8 @@  void bpf_selem_free(struct bpf_local_storage_elem *selem,
 		    struct bpf_local_storage_map *smap,
 		    bool reuse_now)
 {
+	cant_migrate();
+
 	if (!smap->bpf_ma) {
 		/* Only task storage has uptrs and task storage
 		 * has moved to bpf_mem_alloc. Meaning smap->bpf_ma == true
@@ -258,9 +260,7 @@  void bpf_selem_free(struct bpf_local_storage_elem *selem,
 		 * bpf_mem_cache_free will be able to reuse selem
 		 * immediately.
 		 */
-		migrate_disable();
 		bpf_mem_cache_free(&smap->selem_ma, selem);
-		migrate_enable();
 		return;
 	}