bpf: Convert bpf_selem_unlink to failable

To prepare changing both bpf_local_storage_map_bucket::lock and
bpf_local_storage::lock to rqspinlock, convert bpf_selem_unlink() to
failable. It still always succeeds and returns 0 until the change
happens. No functional change.

Open code bpf_selem_unlink_storage() in the only caller,
bpf_selem_unlink(), since unlink_map and unlink_storage must be done
together after all the necessary locks are acquired.

For bpf_local_storage_map_free(), ignore the return from
bpf_selem_unlink() for now. A later patch will allow it to unlink selems
even when failing to acquire locks.

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20260205222916.1788211-5-ameryhung@gmail.com

diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h
index 709506e982a6272c7da9e0e50a69c77164606bb2..f74e0f7656a1c85310a227bdba159f2dc7a19ff8 100644 (file)
--- a/include/linux/bpf_local_storage.h
+++ b/include/linux/bpf_local_storage.h
@@ -176,7 +176,7 @@ int bpf_local_storage_map_check_btf(const struct bpf_map *map,
 void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
                                   struct bpf_local_storage_elem *selem);
 
-void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now);
+int bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now);
 
 int bpf_selem_link_map(struct bpf_local_storage_map *smap,
                       struct bpf_local_storage *local_storage,

diff --git a/kernel/bpf/bpf_cgrp_storage.c b/kernel/bpf/bpf_cgrp_storage.c
index 0687a760974a425e1fa9ec8a8d9ce04571cc7548..8fef24fcac682917a75414f03fbc64938a168650 100644 (file)
--- a/kernel/bpf/bpf_cgrp_storage.c
+++ b/kernel/bpf/bpf_cgrp_storage.c
@@ -118,8 +118,7 @@ static int cgroup_storage_delete(struct cgroup *cgroup, struct bpf_map *map)
        if (!sdata)
                return -ENOENT;
 
-       bpf_selem_unlink(SELEM(sdata), false);
-       return 0;
+       return bpf_selem_unlink(SELEM(sdata), false);
 }
 
 static long bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key)

diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c
index e54cce2b91754c9a03eb840f0bec2247c3c9480e..cedc99184daddb92612467f8f0cd4fd8d50cfb5c 100644 (file)
--- a/kernel/bpf/bpf_inode_storage.c
+++ b/kernel/bpf/bpf_inode_storage.c
@@ -110,9 +110,7 @@ static int inode_storage_delete(struct inode *inode, struct bpf_map *map)
        if (!sdata)
                return -ENOENT;
 
-       bpf_selem_unlink(SELEM(sdata), false);
-
-       return 0;
+       return bpf_selem_unlink(SELEM(sdata), false);
 }
 
 static long bpf_fd_inode_storage_delete_elem(struct bpf_map *map, void *key)

diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 2f94ca4a4475b50bd1c2f05b929bd9a2d505b235..38f5c3db295755e849861cd37036d0c17170a247 100644 (file)
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -308,33 +308,6 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor
        return free_local_storage;
 }
 
-static void bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
-                                    bool reuse_now)
-{
-       struct bpf_local_storage *local_storage;
-       bool free_local_storage = false;
-       HLIST_HEAD(selem_free_list);
-       unsigned long flags;
-
-       if (unlikely(!selem_linked_to_storage_lockless(selem)))
-               /* selem has already been unlinked from sk */
-               return;
-
-       local_storage = rcu_dereference_check(selem->local_storage,
-                                             bpf_rcu_lock_held());
-
-       raw_spin_lock_irqsave(&local_storage->lock, flags);
-       if (likely(selem_linked_to_storage(selem)))
-               free_local_storage = bpf_selem_unlink_storage_nolock(
-                       local_storage, selem, &selem_free_list);
-       raw_spin_unlock_irqrestore(&local_storage->lock, flags);
-
-       bpf_selem_free_list(&selem_free_list, reuse_now);
-
-       if (free_local_storage)
-               bpf_local_storage_free(local_storage, reuse_now);
-}
-
 void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
                                   struct bpf_local_storage_elem *selem)
 {
@@ -386,19 +359,43 @@ static void bpf_selem_link_map_nolock(struct bpf_local_storage_map_bucket *b,
        hlist_add_head_rcu(&selem->map_node, &b->list);
 }
 
-void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now)
+int bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now)
 {
-       int err;
+       struct bpf_local_storage *local_storage;
+       bool free_local_storage = false;
+       HLIST_HEAD(selem_free_list);
+       unsigned long flags;
+       int err = 0;
 
-       /* Always unlink from map before unlinking from local_storage
-        * because selem will be freed after successfully unlinked from
-        * the local_storage.
-        */
-       err = bpf_selem_unlink_map(selem);
-       if (err)
-               return;
+       if (unlikely(!selem_linked_to_storage_lockless(selem)))
+               /* selem has already been unlinked from sk */
+               return 0;
+
+       local_storage = rcu_dereference_check(selem->local_storage,
+                                             bpf_rcu_lock_held());
+
+       raw_spin_lock_irqsave(&local_storage->lock, flags);
+       if (likely(selem_linked_to_storage(selem))) {
+               /* Always unlink from map before unlinking from local_storage
+                * because selem will be freed after successfully unlinked from
+                * the local_storage.
+                */
+               err = bpf_selem_unlink_map(selem);
+               if (err)
+                       goto out;
+
+               free_local_storage = bpf_selem_unlink_storage_nolock(
+                       local_storage, selem, &selem_free_list);
+       }
+out:
+       raw_spin_unlock_irqrestore(&local_storage->lock, flags);
 
-       bpf_selem_unlink_storage(selem, reuse_now);
+       bpf_selem_free_list(&selem_free_list, reuse_now);
+
+       if (free_local_storage)
+               bpf_local_storage_free(local_storage, reuse_now);
+
+       return err;
 }
 
 void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage,

diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c
index a1dc1bf0848a52db08848bb9f70980cca28ec21f..ab902364ac23f2c63507bcc157a96b0efa3bbd72 100644 (file)
--- a/kernel/bpf/bpf_task_storage.c
+++ b/kernel/bpf/bpf_task_storage.c
@@ -167,9 +167,7 @@ static int task_storage_delete(struct task_struct *task, struct bpf_map *map,
        if (!nobusy)
                return -EBUSY;
 
-       bpf_selem_unlink(SELEM(sdata), false);
-
-       return 0;
+       return bpf_selem_unlink(SELEM(sdata), false);
 }
 
 static long bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key)

diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index 0b85d8f2c17eb8bbd1e21c3916c35a22437657d3..d7b5c455199796f0fea8788574168ac726148c16 100644 (file)
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -40,9 +40,7 @@ static int bpf_sk_storage_del(struct sock *sk, struct bpf_map *map)
        if (!sdata)
                return -ENOENT;
 
-       bpf_selem_unlink(SELEM(sdata), false);
-
-       return 0;
+       return bpf_selem_unlink(SELEM(sdata), false);
 }
 
 /* Called by __sk_destruct() & bpf_sk_storage_clone() */