bpf_local_storage_update() takes the map bucket lock while holding local_storage->lock. bpf_selem_unlink_map() does the same; its only caller holds local_storage->lock. The outer lock is acquired with raw_res_spin_lock_irqsave(), so interrupts are already disabled at both sites. Using raw_res_spin_lock_irqsave() for the nested lock saves the already disabled IRQ state and issues another IRQ disable. The matching unlock tests that saved state before leaving interrupts disabled. On x86-64, this adds a pushfq/popq/cli sequence and a test/branch around an unreachable sti to each acquisition. Use raw_res_spin_lock() and raw_res_spin_unlock() instead. They retain preemption nesting, memory ordering and resilient-lock bookkeeping. The outer unlock remains responsible for restoring the caller's IRQ state. In the tested clang x86-64 build, this removes five executed instructions from each uncontended nested acquisition. It also shrinks bpf_local_storage_update() from 1732 to 1702 bytes and bpf_selem_unlink() from 1030 to 992 bytes. The affected paths are updates that add or replace an element in existing owner storage and successful unlinks. Document the owner-lock requirement of bpf_selem_unlink_map() and assert that interrupts are disabled. Signed-off-by: Usama Arif --- kernel/bpf/bpf_local_storage.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index 6fc6a4b672b55..4642da062f0f8 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -240,24 +240,26 @@ void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage, hlist_add_head_rcu(&selem->snode, &local_storage->list); } +/* Must be called with the owning local_storage->lock held. */ static int bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) { struct bpf_local_storage *local_storage; struct bpf_local_storage_map *smap; struct bpf_local_storage_map_bucket *b; - unsigned long flags; int err; + lockdep_assert_irqs_disabled(); + local_storage = rcu_dereference_check(selem->local_storage, bpf_rcu_lock_held()); smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held()); b = select_bucket(smap, local_storage); - err = raw_res_spin_lock_irqsave(&b->lock, flags); + err = raw_res_spin_lock(&b->lock); if (err) return err; hlist_del_init_rcu(&selem->map_node); - raw_res_spin_unlock_irqrestore(&b->lock, flags); + raw_res_spin_unlock(&b->lock); return 0; } @@ -552,7 +554,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, struct bpf_local_storage *local_storage; struct bpf_local_storage_map_bucket *b; HLIST_HEAD(old_selem_free_list); - unsigned long flags, b_flags; + unsigned long flags; int err; /* BPF_EXIST and BPF_NOEXIST cannot be both set */ @@ -637,7 +639,8 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, b = select_bucket(smap, local_storage); - err = raw_res_spin_lock_irqsave(&b->lock, b_flags); + /* local_storage->lock is held, so IRQs are already disabled. */ + err = raw_res_spin_lock(&b->lock); if (err) goto unlock; @@ -655,7 +658,7 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, &old_selem_free_list); } - raw_res_spin_unlock_irqrestore(&b->lock, b_flags); + raw_res_spin_unlock(&b->lock); unlock: raw_res_spin_unlock_irqrestore(&local_storage->lock, flags); free_selem: -- 2.53.0-Meta