From 7f49800a2c246e289669186fd1f1aad829616c24 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:40 -0700 Subject: [PATCH 01/12] bpf: Select bpf_local_storage_map_bucket based on bpf_local_storage A later bpf_local_storage refactor will acquire all locks before performing any update. To simplified the number of locks needed to take in bpf_local_storage_map_update(), determine the bucket based on the local_storage an selem belongs to instead of the selem pointer. Currently, when a new selem needs to be created to replace the old selem in bpf_local_storage_map_update(), locks of both buckets need to be acquired to prevent racing. This can be simplified if the two selem belongs to the same bucket so that only one bucket needs to be locked. Therefore, instead of hashing selem, hashing the local_storage pointer the selem belongs. This is safe since a selem is always linked to local_storage before linked to map and unlinked from local_storage after unlinked from map. Performance wise, this is slightly better as update now requires locking one bucket. It should not change the level of contention on one bucket as the pointers to local storages of selems in a map are just as unique as pointers to selems. Signed-off-by: Amery Hung --- kernel/bpf/bpf_local_storage.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index b931fbceb54da..e4a7cd33b455a 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -19,9 +19,9 @@ static struct bpf_local_storage_map_bucket * select_bucket(struct bpf_local_storage_map *smap, - struct bpf_local_storage_elem *selem) + struct bpf_local_storage *local_storage) { - return &smap->buckets[hash_ptr(selem, smap->bucket_log)]; + return &smap->buckets[hash_ptr(local_storage, smap->bucket_log)]; } static int mem_charge(struct bpf_local_storage_map *smap, void *owner, u32 size) @@ -411,6 +411,7 @@ void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage, static void 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; @@ -419,8 +420,10 @@ static void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) /* selem has already be unlinked from smap */ return; + 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, selem); + b = select_bucket(smap, local_storage); raw_spin_lock_irqsave(&b->lock, flags); if (likely(selem_linked_to_map(selem))) hlist_del_init_rcu(&selem->map_node); @@ -430,9 +433,13 @@ static void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) void bpf_selem_link_map(struct bpf_local_storage_map *smap, struct bpf_local_storage_elem *selem) { - struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem); + struct bpf_local_storage *local_storage; + struct bpf_local_storage_map_bucket *b; unsigned long flags; + local_storage = rcu_dereference_check(selem->local_storage, + bpf_rcu_lock_held()); + b = select_bucket(smap, local_storage); raw_spin_lock_irqsave(&b->lock, flags); RCU_INIT_POINTER(SDATA(selem)->smap, smap); hlist_add_head_rcu(&selem->map_node, &b->list); From 9da132d9a3d4efab58ec918913cf000fcb69236e Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:41 -0700 Subject: [PATCH 02/12] bpf: Convert bpf_selem_unlink_map to failable To prepare for changing bpf_local_storage_map_bucket::lock to rqspinlock, convert bpf_selem_unlink_map() to failable. It still always succeeds and returns 0 for now. Since some operations updating local storage cannot fail in the middle, open-code bpf_selem_unlink_map() to take the b->lock before the operation. There are two such locations: - bpf_local_storage_alloc() The first selem will be unlinked from smap if cmpxchg owner_storage_ptr fails, which should not fail. Therefore, hold b->lock when linking until allocation complete. Helpers that assume b->lock is held by callers are introduced: bpf_selem_link_map_nolock() and bpf_selem_unlink_map_nolock(). - bpf_local_storage_update() The three step update process: link_map(new_selem), link_storage(new_selem), and unlink_map(old_selem) should not fail in the middle. In bpf_selem_unlink(), bpf_selem_unlink_map() and bpf_selem_unlink_storage() should either all succeed or fail as a whole instead of failing in the middle. So, return if unlink_map() failed. In bpf_local_storage_destroy(), since it cannot deadlock with itself or bpf_local_storage_map_free() who the function might be racing with, retry if bpf_selem_unlink_map() fails due to rqspinlock returning errors. Signed-off-by: Amery Hung --- kernel/bpf/bpf_local_storage.c | 54 ++++++++++++++++++++++++++++------ 1 file changed, 45 insertions(+), 9 deletions(-) diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index e4a7cd33b455a..cbccf6b77f10a 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -409,7 +409,7 @@ void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage, hlist_add_head_rcu(&selem->snode, &local_storage->list); } -static void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) +static int bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) { struct bpf_local_storage *local_storage; struct bpf_local_storage_map *smap; @@ -418,7 +418,7 @@ static void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) if (unlikely(!selem_linked_to_map_lockless(selem))) /* selem has already be unlinked from smap */ - return; + return 0; local_storage = rcu_dereference_check(selem->local_storage, bpf_rcu_lock_held()); @@ -428,6 +428,14 @@ static void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) if (likely(selem_linked_to_map(selem))) hlist_del_init_rcu(&selem->map_node); raw_spin_unlock_irqrestore(&b->lock, flags); + + return 0; +} + +static void bpf_selem_unlink_map_nolock(struct bpf_local_storage_elem *selem) +{ + if (likely(selem_linked_to_map(selem))) + hlist_del_init_rcu(&selem->map_node); } void bpf_selem_link_map(struct bpf_local_storage_map *smap, @@ -446,13 +454,26 @@ void bpf_selem_link_map(struct bpf_local_storage_map *smap, raw_spin_unlock_irqrestore(&b->lock, flags); } +static void bpf_selem_link_map_nolock(struct bpf_local_storage_map *smap, + struct bpf_local_storage_elem *selem, + struct bpf_local_storage_map_bucket *b) +{ + RCU_INIT_POINTER(SDATA(selem)->smap, smap); + hlist_add_head_rcu(&selem->map_node, &b->list); +} + void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now) { + int err; + /* Always unlink from map before unlinking from local_storage * because selem will be freed after successfully unlinked from * the local_storage. */ - bpf_selem_unlink_map(selem); + err = bpf_selem_unlink_map(selem); + if (err) + return; + bpf_selem_unlink_storage(selem, reuse_now); } @@ -494,6 +515,8 @@ int bpf_local_storage_alloc(void *owner, { struct bpf_local_storage *prev_storage, *storage; struct bpf_local_storage **owner_storage_ptr; + struct bpf_local_storage_map_bucket *b; + unsigned long flags; int err; err = mem_charge(smap, owner, sizeof(*storage)); @@ -516,7 +539,10 @@ int bpf_local_storage_alloc(void *owner, storage->owner = owner; bpf_selem_link_storage_nolock(storage, first_selem); - bpf_selem_link_map(smap, first_selem); + + b = select_bucket(smap, storage); + raw_spin_lock_irqsave(&b->lock, flags); + bpf_selem_link_map_nolock(smap, first_selem, b); owner_storage_ptr = (struct bpf_local_storage **)owner_storage(smap, owner); @@ -532,7 +558,8 @@ int bpf_local_storage_alloc(void *owner, */ prev_storage = cmpxchg(owner_storage_ptr, NULL, storage); if (unlikely(prev_storage)) { - bpf_selem_unlink_map(first_selem); + bpf_selem_unlink_map_nolock(first_selem); + raw_spin_unlock_irqrestore(&b->lock, flags); err = -EAGAIN; goto uncharge; @@ -546,6 +573,7 @@ int bpf_local_storage_alloc(void *owner, * bucket->list under rcu_read_lock(). */ } + raw_spin_unlock_irqrestore(&b->lock, flags); return 0; @@ -567,8 +595,9 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, struct bpf_local_storage_data *old_sdata = NULL; struct bpf_local_storage_elem *alloc_selem, *selem = NULL; struct bpf_local_storage *local_storage; + struct bpf_local_storage_map_bucket *b; HLIST_HEAD(old_selem_free_list); - unsigned long flags; + unsigned long flags, b_flags; int err; /* BPF_EXIST and BPF_NOEXIST cannot be both set */ @@ -652,20 +681,26 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, goto unlock; } + b = select_bucket(smap, local_storage); + + raw_spin_lock_irqsave(&b->lock, b_flags); + alloc_selem = NULL; /* First, link the new selem to the map */ - bpf_selem_link_map(smap, selem); + bpf_selem_link_map_nolock(smap, selem, b); /* Second, link (and publish) the new selem to local_storage */ bpf_selem_link_storage_nolock(local_storage, selem); /* Third, remove old selem, SELEM(old_sdata) */ if (old_sdata) { - bpf_selem_unlink_map(SELEM(old_sdata)); + bpf_selem_unlink_map_nolock(SELEM(old_sdata)); bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata), true, &old_selem_free_list); } + raw_spin_unlock_irqrestore(&b->lock, b_flags); + unlock: raw_spin_unlock_irqrestore(&local_storage->lock, flags); bpf_selem_free_list(&old_selem_free_list, false); @@ -743,6 +778,7 @@ void bpf_local_storage_destroy(struct bpf_local_storage *local_storage) HLIST_HEAD(free_selem_list); struct hlist_node *n; unsigned long flags; + int err; storage_smap = rcu_dereference_check(local_storage->smap, bpf_rcu_lock_held()); bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, NULL); @@ -761,7 +797,7 @@ void bpf_local_storage_destroy(struct bpf_local_storage *local_storage) /* Always unlink from map before unlinking from * local_storage. */ - bpf_selem_unlink_map(selem); + while (bpf_selem_unlink_map(selem)); /* If local_storage list has only one element, the * bpf_selem_unlink_storage_nolock() will return true. * Otherwise, it will return false. The current loop iteration From 17093b9a257383ade7b4562156177063077fccfd Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:42 -0700 Subject: [PATCH 03/12] bpf: Convert bpf_selem_link_map to failable To prepare for changing bpf_local_storage_map_bucket::lock to rqspinlock, convert bpf_selem_link_map() to failable. It still always succeeds and returns 0 until the change happens. No functional change. __must_check is added to the function declaration locally to make sure all the callers are accounted for during the conversion. Signed-off-by: Amery Hung --- include/linux/bpf_local_storage.h | 4 ++-- kernel/bpf/bpf_local_storage.c | 6 ++++-- net/core/bpf_sk_storage.c | 4 +++- 3 files changed, 9 insertions(+), 5 deletions(-) diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h index ab7244d8108f6..dc56fa459ac9d 100644 --- a/include/linux/bpf_local_storage.h +++ b/include/linux/bpf_local_storage.h @@ -182,8 +182,8 @@ void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage, void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now); -void bpf_selem_link_map(struct bpf_local_storage_map *smap, - struct bpf_local_storage_elem *selem); +int bpf_selem_link_map(struct bpf_local_storage_map *smap, + struct bpf_local_storage_elem *selem); struct bpf_local_storage_elem * bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, void *value, diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index cbccf6b77f10a..682409fb22a2a 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -438,8 +438,8 @@ static void bpf_selem_unlink_map_nolock(struct bpf_local_storage_elem *selem) hlist_del_init_rcu(&selem->map_node); } -void bpf_selem_link_map(struct bpf_local_storage_map *smap, - struct bpf_local_storage_elem *selem) +int bpf_selem_link_map(struct bpf_local_storage_map *smap, + struct bpf_local_storage_elem *selem) { struct bpf_local_storage *local_storage; struct bpf_local_storage_map_bucket *b; @@ -452,6 +452,8 @@ void bpf_selem_link_map(struct bpf_local_storage_map *smap, RCU_INIT_POINTER(SDATA(selem)->smap, smap); hlist_add_head_rcu(&selem->map_node, &b->list); raw_spin_unlock_irqrestore(&b->lock, flags); + + return 0; } static void bpf_selem_link_map_nolock(struct bpf_local_storage_map *smap, diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c index 2e538399757fe..fac5cf3857859 100644 --- a/net/core/bpf_sk_storage.c +++ b/net/core/bpf_sk_storage.c @@ -194,7 +194,9 @@ int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk) } if (new_sk_storage) { - bpf_selem_link_map(smap, copy_selem); + ret = bpf_selem_link_map(smap, copy_selem); + if (ret) + goto out; bpf_selem_link_storage_nolock(new_sk_storage, copy_selem); } else { ret = bpf_local_storage_alloc(newsk, smap, copy_selem, GFP_ATOMIC); From ff431d9af515d55cc7ae18d5467d4aaac6ed3a08 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:43 -0700 Subject: [PATCH 04/12] bpf: Open code bpf_selem_unlink_storage in bpf_selem_unlink To prepare for changing bpf_local_storage::lock to rqspinlock, 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. Signed-off-by: Amery Hung --- kernel/bpf/bpf_local_storage.c | 71 ++++++++++++++++------------------ 1 file changed, 33 insertions(+), 38 deletions(-) diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index 682409fb22a2a..9c2b041ae9ca1 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -371,37 +371,6 @@ static bool check_storage_bpf_ma(struct bpf_local_storage *local_storage, return selem_smap->bpf_ma; } -static void bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem, - bool reuse_now) -{ - struct bpf_local_storage_map *storage_smap; - struct bpf_local_storage *local_storage; - bool bpf_ma, 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()); - storage_smap = rcu_dereference_check(local_storage->smap, - bpf_rcu_lock_held()); - bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, selem); - - 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, true, &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, storage_smap, bpf_ma, reuse_now); -} - void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage, struct bpf_local_storage_elem *selem) { @@ -466,17 +435,43 @@ static void bpf_selem_link_map_nolock(struct bpf_local_storage_map *smap, void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now) { + struct bpf_local_storage_map *storage_smap; + struct bpf_local_storage *local_storage; + bool bpf_ma, free_local_storage = false; + HLIST_HEAD(selem_free_list); + unsigned long flags; int err; - /* 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) + if (unlikely(!selem_linked_to_storage_lockless(selem))) + /* selem has already been unlinked from sk */ return; - bpf_selem_unlink_storage(selem, reuse_now); + local_storage = rcu_dereference_check(selem->local_storage, + bpf_rcu_lock_held()); + storage_smap = rcu_dereference_check(local_storage->smap, + bpf_rcu_lock_held()); + bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, selem); + + 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, true, &selem_free_list); + } +out: + 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, storage_smap, bpf_ma, reuse_now); } void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage, From 428095d4296fa1b84e0771ca1f31c2aaf540f39c Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:44 -0700 Subject: [PATCH 05/12] 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. For bpf_local_storage_map_free(), since it cannot deadlock with itself or bpf_local_storage_destroy who the function might be racing with, retry if bpf_selem_unlink() fails due to rqspinlock returning errors. __must_check is added to the function declaration locally to make sure all callers are accounted for during the conversion. Signed-off-by: Amery Hung --- include/linux/bpf_local_storage.h | 2 +- kernel/bpf/bpf_cgrp_storage.c | 3 +-- kernel/bpf/bpf_inode_storage.c | 4 +--- kernel/bpf/bpf_local_storage.c | 6 ++++-- kernel/bpf/bpf_task_storage.c | 4 +--- net/core/bpf_sk_storage.c | 4 +--- 6 files changed, 9 insertions(+), 14 deletions(-) diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h index dc56fa459ac9d..26b7f53dad336 100644 --- a/include/linux/bpf_local_storage.h +++ b/include/linux/bpf_local_storage.h @@ -180,7 +180,7 @@ 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_elem *selem); diff --git a/kernel/bpf/bpf_cgrp_storage.c b/kernel/bpf/bpf_cgrp_storage.c index 0687a760974a4..8fef24fcac682 100644 --- 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 e54cce2b91754..cedc99184dadd 100644 --- 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 9c2b041ae9ca1..e0e405060e3c6 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -433,7 +433,7 @@ static void bpf_selem_link_map_nolock(struct bpf_local_storage_map *smap, 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) { struct bpf_local_storage_map *storage_smap; struct bpf_local_storage *local_storage; @@ -472,6 +472,8 @@ void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now) if (free_local_storage) bpf_local_storage_free(local_storage, storage_smap, bpf_ma, reuse_now); + + return 0; } void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage, @@ -930,7 +932,7 @@ void bpf_local_storage_map_free(struct bpf_map *map, struct bpf_local_storage_elem, map_node))) { if (busy_counter) this_cpu_inc(*busy_counter); - bpf_selem_unlink(selem, true); + while (bpf_selem_unlink(selem, true)); if (busy_counter) this_cpu_dec(*busy_counter); cond_resched_rcu(); diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c index a1dc1bf0848a5..ab902364ac23f 100644 --- 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 fac5cf3857859..7b3d44667ceec 100644 --- 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() */ From a97c5daf0fd07d5ba24b3729cdc6cd415cb016b5 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:45 -0700 Subject: [PATCH 06/12] bpf: Change local_storage->lock and b->lock to rqspinlock Change bpf_local_storage::lock and bpf_local_storage_map_bucket::lock to from raw_spin_lock to rqspinlock. Finally, propagate errors from raw_res_spin_lock_irqsave() to syscall return or BPF helper return. In bpf_local_storage_destroy(), since it cannot deadlock with itself or bpf_local_storage_map_free() who the function might be racing with, retry if bpf_selem_unlink_map() fails due to rqspinlock returning errors For, __bpf_local_storage_map_cache(), instead of handling the error, skip updating the cache. Signed-off-by: Amery Hung --- include/linux/bpf_local_storage.h | 5 ++- kernel/bpf/bpf_local_storage.c | 65 ++++++++++++++++++++----------- 2 files changed, 46 insertions(+), 24 deletions(-) diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h index 26b7f53dad336..2a0aae5168fa8 100644 --- a/include/linux/bpf_local_storage.h +++ b/include/linux/bpf_local_storage.h @@ -15,6 +15,7 @@ #include #include #include +#include #define BPF_LOCAL_STORAGE_CACHE_SIZE 16 @@ -23,7 +24,7 @@ rcu_read_lock_bh_held()) struct bpf_local_storage_map_bucket { struct hlist_head list; - raw_spinlock_t lock; + rqspinlock_t lock; }; /* Thp map is not the primary owner of a bpf_local_storage_elem. @@ -99,7 +100,7 @@ struct bpf_local_storage { * bpf_local_storage_elem. */ struct rcu_head rcu; - raw_spinlock_t lock; /* Protect adding/removing from the "list" */ + rqspinlock_t lock; /* Protect adding/removing from the "list" */ }; /* U16_MAX is much more than enough for sk local storage diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index e0e405060e3c6..572956e2a72d1 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -384,6 +384,7 @@ static int bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) struct bpf_local_storage_map *smap; struct bpf_local_storage_map_bucket *b; unsigned long flags; + int err; if (unlikely(!selem_linked_to_map_lockless(selem))) /* selem has already be unlinked from smap */ @@ -393,10 +394,13 @@ static int bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) bpf_rcu_lock_held()); smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held()); b = select_bucket(smap, local_storage); - raw_spin_lock_irqsave(&b->lock, flags); + err = raw_res_spin_lock_irqsave(&b->lock, flags); + if (err) + return err; + if (likely(selem_linked_to_map(selem))) hlist_del_init_rcu(&selem->map_node); - raw_spin_unlock_irqrestore(&b->lock, flags); + raw_res_spin_unlock_irqrestore(&b->lock, flags); return 0; } @@ -413,14 +417,18 @@ int bpf_selem_link_map(struct bpf_local_storage_map *smap, struct bpf_local_storage *local_storage; struct bpf_local_storage_map_bucket *b; unsigned long flags; + int err; local_storage = rcu_dereference_check(selem->local_storage, bpf_rcu_lock_held()); b = select_bucket(smap, local_storage); - raw_spin_lock_irqsave(&b->lock, flags); + err = raw_res_spin_lock_irqsave(&b->lock, flags); + if (err) + return err; + RCU_INIT_POINTER(SDATA(selem)->smap, smap); hlist_add_head_rcu(&selem->map_node, &b->list); - raw_spin_unlock_irqrestore(&b->lock, flags); + raw_res_spin_unlock_irqrestore(&b->lock, flags); return 0; } @@ -444,7 +452,7 @@ int bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now) if (unlikely(!selem_linked_to_storage_lockless(selem))) /* selem has already been unlinked from sk */ - return; + return 0; local_storage = rcu_dereference_check(selem->local_storage, bpf_rcu_lock_held()); @@ -452,7 +460,10 @@ int bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now) bpf_rcu_lock_held()); bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, selem); - raw_spin_lock_irqsave(&local_storage->lock, flags); + err = raw_res_spin_lock_irqsave(&local_storage->lock, flags); + if (err) + return err; + 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 @@ -466,14 +477,14 @@ int bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now) local_storage, selem, true, &selem_free_list); } out: - raw_spin_unlock_irqrestore(&local_storage->lock, flags); + raw_res_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, storage_smap, bpf_ma, reuse_now); - return 0; + return err; } void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage, @@ -481,16 +492,20 @@ void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage, struct bpf_local_storage_elem *selem) { unsigned long flags; + int err; /* spinlock is needed to avoid racing with the * parallel delete. Otherwise, publishing an already * deleted sdata to the cache will become a use-after-free * problem in the next bpf_local_storage_lookup(). */ - raw_spin_lock_irqsave(&local_storage->lock, flags); + err = raw_res_spin_lock_irqsave(&local_storage->lock, flags); + if (err) + return; + if (selem_linked_to_storage(selem)) rcu_assign_pointer(local_storage->cache[smap->cache_idx], SDATA(selem)); - raw_spin_unlock_irqrestore(&local_storage->lock, flags); + raw_res_spin_unlock_irqrestore(&local_storage->lock, flags); } static int check_flags(const struct bpf_local_storage_data *old_sdata, @@ -534,13 +549,16 @@ int bpf_local_storage_alloc(void *owner, RCU_INIT_POINTER(storage->smap, smap); INIT_HLIST_HEAD(&storage->list); - raw_spin_lock_init(&storage->lock); + raw_res_spin_lock_init(&storage->lock); storage->owner = owner; bpf_selem_link_storage_nolock(storage, first_selem); b = select_bucket(smap, storage); - raw_spin_lock_irqsave(&b->lock, flags); + err = raw_res_spin_lock_irqsave(&b->lock, flags); + if (err) + goto uncharge; + bpf_selem_link_map_nolock(smap, first_selem, b); owner_storage_ptr = @@ -558,7 +576,7 @@ int bpf_local_storage_alloc(void *owner, prev_storage = cmpxchg(owner_storage_ptr, NULL, storage); if (unlikely(prev_storage)) { bpf_selem_unlink_map_nolock(first_selem); - raw_spin_unlock_irqrestore(&b->lock, flags); + raw_res_spin_unlock_irqrestore(&b->lock, flags); err = -EAGAIN; goto uncharge; @@ -572,7 +590,7 @@ int bpf_local_storage_alloc(void *owner, * bucket->list under rcu_read_lock(). */ } - raw_spin_unlock_irqrestore(&b->lock, flags); + raw_res_spin_unlock_irqrestore(&b->lock, flags); return 0; @@ -655,7 +673,9 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, if (!alloc_selem) return ERR_PTR(-ENOMEM); - raw_spin_lock_irqsave(&local_storage->lock, flags); + err = raw_res_spin_lock_irqsave(&local_storage->lock, flags); + if (err) + return ERR_PTR(err); /* Recheck local_storage->list under local_storage->lock */ if (unlikely(hlist_empty(&local_storage->list))) { @@ -682,7 +702,9 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, b = select_bucket(smap, local_storage); - raw_spin_lock_irqsave(&b->lock, b_flags); + err = raw_res_spin_lock_irqsave(&b->lock, b_flags); + if (err) + goto unlock; alloc_selem = NULL; /* First, link the new selem to the map */ @@ -698,10 +720,9 @@ bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, true, &old_selem_free_list); } - raw_spin_unlock_irqrestore(&b->lock, b_flags); - + raw_res_spin_unlock_irqrestore(&b->lock, b_flags); unlock: - raw_spin_unlock_irqrestore(&local_storage->lock, flags); + raw_res_spin_unlock_irqrestore(&local_storage->lock, flags); bpf_selem_free_list(&old_selem_free_list, false); if (alloc_selem) { mem_uncharge(smap, owner, smap->elem_size); @@ -791,7 +812,7 @@ void bpf_local_storage_destroy(struct bpf_local_storage *local_storage) * when unlinking elem from the local_storage->list and * the map's bucket->list. */ - raw_spin_lock_irqsave(&local_storage->lock, flags); + while (raw_res_spin_lock_irqsave(&local_storage->lock, flags)); hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) { /* Always unlink from map before unlinking from * local_storage. @@ -806,7 +827,7 @@ void bpf_local_storage_destroy(struct bpf_local_storage *local_storage) free_storage = bpf_selem_unlink_storage_nolock( local_storage, selem, true, &free_selem_list); } - raw_spin_unlock_irqrestore(&local_storage->lock, flags); + raw_res_spin_unlock_irqrestore(&local_storage->lock, flags); bpf_selem_free_list(&free_selem_list, true); @@ -863,7 +884,7 @@ bpf_local_storage_map_alloc(union bpf_attr *attr, for (i = 0; i < nbuckets; i++) { INIT_HLIST_HEAD(&smap->buckets[i].list); - raw_spin_lock_init(&smap->buckets[i].lock); + raw_res_spin_lock_init(&smap->buckets[i].lock); } smap->elem_size = offsetof(struct bpf_local_storage_elem, From c6dd171a7a71aef6c60b7b46c54dd17fd0269915 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:46 -0700 Subject: [PATCH 07/12] bpf: Remove task local storage percpu counter The percpu counter in task local storage is no longer needed as the underlying bpf_local_storage can now handle deadlock with the help of rqspinlock. Remove the percpu counter and related migrate_{disable, enable}. Since the percpu counter is removed, merge back bpf_task_storage_get() and bpf_task_storage_get_recur(). This will allow the bpf syscalls and helpers to run concurrently on the same CPU, removing the spurious -EBUSY error. bpf_task_storage_get(..., F_CREATE) will now always succeed with enough free memory unless being called recursively. Signed-off-by: Amery Hung --- kernel/bpf/bpf_task_storage.c | 150 ++++------------------------------ kernel/bpf/helpers.c | 4 - 2 files changed, 18 insertions(+), 136 deletions(-) diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c index ab902364ac23f..dd858226ada2d 100644 --- a/kernel/bpf/bpf_task_storage.c +++ b/kernel/bpf/bpf_task_storage.c @@ -20,29 +20,6 @@ DEFINE_BPF_STORAGE_CACHE(task_cache); -static DEFINE_PER_CPU(int, bpf_task_storage_busy); - -static void bpf_task_storage_lock(void) -{ - cant_migrate(); - this_cpu_inc(bpf_task_storage_busy); -} - -static void bpf_task_storage_unlock(void) -{ - this_cpu_dec(bpf_task_storage_busy); -} - -static bool bpf_task_storage_trylock(void) -{ - cant_migrate(); - if (unlikely(this_cpu_inc_return(bpf_task_storage_busy) != 1)) { - this_cpu_dec(bpf_task_storage_busy); - return false; - } - return true; -} - static struct bpf_local_storage __rcu **task_storage_ptr(void *owner) { struct task_struct *task = owner; @@ -70,17 +47,15 @@ void bpf_task_storage_free(struct task_struct *task) { struct bpf_local_storage *local_storage; - rcu_read_lock_dont_migrate(); + rcu_read_lock(); local_storage = rcu_dereference(task->bpf_storage); if (!local_storage) goto out; - bpf_task_storage_lock(); bpf_local_storage_destroy(local_storage); - bpf_task_storage_unlock(); out: - rcu_read_unlock_migrate(); + rcu_read_unlock(); } static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key) @@ -106,9 +81,7 @@ static void *bpf_pid_task_storage_lookup_elem(struct bpf_map *map, void *key) goto out; } - bpf_task_storage_lock(); sdata = task_storage_lookup(task, map, true); - bpf_task_storage_unlock(); put_pid(pid); return sdata ? sdata->data : NULL; out: @@ -143,11 +116,9 @@ static long bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key, goto out; } - bpf_task_storage_lock(); sdata = bpf_local_storage_update( task, (struct bpf_local_storage_map *)map, value, map_flags, true, GFP_ATOMIC); - bpf_task_storage_unlock(); err = PTR_ERR_OR_ZERO(sdata); out: @@ -155,8 +126,7 @@ static long bpf_pid_task_storage_update_elem(struct bpf_map *map, void *key, return err; } -static int task_storage_delete(struct task_struct *task, struct bpf_map *map, - bool nobusy) +static int task_storage_delete(struct task_struct *task, struct bpf_map *map) { struct bpf_local_storage_data *sdata; @@ -164,9 +134,6 @@ static int task_storage_delete(struct task_struct *task, struct bpf_map *map, if (!sdata) return -ENOENT; - if (!nobusy) - return -EBUSY; - return bpf_selem_unlink(SELEM(sdata), false); } @@ -192,111 +159,50 @@ static long bpf_pid_task_storage_delete_elem(struct bpf_map *map, void *key) goto out; } - bpf_task_storage_lock(); - err = task_storage_delete(task, map, true); - bpf_task_storage_unlock(); + err = task_storage_delete(task, map); out: put_pid(pid); return err; } -/* Called by bpf_task_storage_get*() helpers */ -static void *__bpf_task_storage_get(struct bpf_map *map, - struct task_struct *task, void *value, - u64 flags, gfp_t gfp_flags, bool nobusy) +/* *gfp_flags* is a hidden argument provided by the verifier */ +BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *, + task, void *, value, u64, flags, gfp_t, gfp_flags) { struct bpf_local_storage_data *sdata; - sdata = task_storage_lookup(task, map, nobusy); + WARN_ON_ONCE(!bpf_rcu_lock_held()); + if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task) + return (unsigned long)NULL; + + sdata = task_storage_lookup(task, map, true); if (sdata) - return sdata->data; + return (unsigned long)sdata->data; /* only allocate new storage, when the task is refcounted */ if (refcount_read(&task->usage) && - (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) && nobusy) { + (flags & BPF_LOCAL_STORAGE_GET_F_CREATE)) { sdata = bpf_local_storage_update( task, (struct bpf_local_storage_map *)map, value, BPF_NOEXIST, false, gfp_flags); - return IS_ERR(sdata) ? NULL : sdata->data; + return IS_ERR(sdata) ? (unsigned long)NULL : (unsigned long)sdata->data; } - return NULL; -} - -/* *gfp_flags* is a hidden argument provided by the verifier */ -BPF_CALL_5(bpf_task_storage_get_recur, struct bpf_map *, map, struct task_struct *, - task, void *, value, u64, flags, gfp_t, gfp_flags) -{ - bool nobusy; - void *data; - - WARN_ON_ONCE(!bpf_rcu_lock_held()); - if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task) - return (unsigned long)NULL; - - nobusy = bpf_task_storage_trylock(); - data = __bpf_task_storage_get(map, task, value, flags, - gfp_flags, nobusy); - if (nobusy) - bpf_task_storage_unlock(); - return (unsigned long)data; -} - -/* *gfp_flags* is a hidden argument provided by the verifier */ -BPF_CALL_5(bpf_task_storage_get, struct bpf_map *, map, struct task_struct *, - task, void *, value, u64, flags, gfp_t, gfp_flags) -{ - void *data; - - WARN_ON_ONCE(!bpf_rcu_lock_held()); - if (flags & ~BPF_LOCAL_STORAGE_GET_F_CREATE || !task) - return (unsigned long)NULL; - - bpf_task_storage_lock(); - data = __bpf_task_storage_get(map, task, value, flags, - gfp_flags, true); - bpf_task_storage_unlock(); - return (unsigned long)data; -} - -BPF_CALL_2(bpf_task_storage_delete_recur, struct bpf_map *, map, struct task_struct *, - task) -{ - bool nobusy; - int ret; - - WARN_ON_ONCE(!bpf_rcu_lock_held()); - if (!task) - return -EINVAL; - - nobusy = bpf_task_storage_trylock(); - /* This helper must only be called from places where the lifetime of the task - * is guaranteed. Either by being refcounted or by being protected - * by an RCU read-side critical section. - */ - ret = task_storage_delete(task, map, nobusy); - if (nobusy) - bpf_task_storage_unlock(); - return ret; + return (unsigned long)NULL; } BPF_CALL_2(bpf_task_storage_delete, struct bpf_map *, map, struct task_struct *, task) { - int ret; - WARN_ON_ONCE(!bpf_rcu_lock_held()); if (!task) return -EINVAL; - bpf_task_storage_lock(); /* This helper must only be called from places where the lifetime of the task * is guaranteed. Either by being refcounted or by being protected * by an RCU read-side critical section. */ - ret = task_storage_delete(task, map, true); - bpf_task_storage_unlock(); - return ret; + return task_storage_delete(task, map); } static int notsupp_get_next_key(struct bpf_map *map, void *key, void *next_key) @@ -311,7 +217,7 @@ static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr) static void task_storage_map_free(struct bpf_map *map) { - bpf_local_storage_map_free(map, &task_cache, &bpf_task_storage_busy); + bpf_local_storage_map_free(map, &task_cache, NULL); } BTF_ID_LIST_GLOBAL_SINGLE(bpf_local_storage_map_btf_id, struct, bpf_local_storage_map) @@ -330,17 +236,6 @@ const struct bpf_map_ops task_storage_map_ops = { .map_owner_storage_ptr = task_storage_ptr, }; -const struct bpf_func_proto bpf_task_storage_get_recur_proto = { - .func = bpf_task_storage_get_recur, - .gpl_only = false, - .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, - .arg1_type = ARG_CONST_MAP_PTR, - .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, - .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], - .arg3_type = ARG_PTR_TO_MAP_VALUE_OR_NULL, - .arg4_type = ARG_ANYTHING, -}; - const struct bpf_func_proto bpf_task_storage_get_proto = { .func = bpf_task_storage_get, .gpl_only = false, @@ -352,15 +247,6 @@ const struct bpf_func_proto bpf_task_storage_get_proto = { .arg4_type = ARG_ANYTHING, }; -const struct bpf_func_proto bpf_task_storage_delete_recur_proto = { - .func = bpf_task_storage_delete_recur, - .gpl_only = false, - .ret_type = RET_INTEGER, - .arg1_type = ARG_CONST_MAP_PTR, - .arg2_type = ARG_PTR_TO_BTF_ID_OR_NULL, - .arg2_btf_id = &btf_tracing_ids[BTF_TRACING_TYPE_TASK], -}; - const struct bpf_func_proto bpf_task_storage_delete_proto = { .func = bpf_task_storage_delete, .gpl_only = false, diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index c9fab9a356dfc..1d83f29a8986d 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2040,12 +2040,8 @@ bpf_base_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_get_cgroup_classid_curr_proto; #endif case BPF_FUNC_task_storage_get: - if (bpf_prog_check_recur(prog)) - return &bpf_task_storage_get_recur_proto; return &bpf_task_storage_get_proto; case BPF_FUNC_task_storage_delete: - if (bpf_prog_check_recur(prog)) - return &bpf_task_storage_delete_recur_proto; return &bpf_task_storage_delete_proto; default: break; From 2917c64fb850da4f9b8871e82c5f97bc8ea03815 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:47 -0700 Subject: [PATCH 08/12] bpf: Remove cgroup local storage percpu counter The percpu counter in cgroup local storage is no longer needed as the underlying bpf_local_storage can now handle deadlock with the help of rqspinlock. Remove the percpu counter and related migrate_{disable, enable}. Signed-off-by: Amery Hung --- kernel/bpf/bpf_cgrp_storage.c | 59 +++++------------------------------ 1 file changed, 8 insertions(+), 51 deletions(-) diff --git a/kernel/bpf/bpf_cgrp_storage.c b/kernel/bpf/bpf_cgrp_storage.c index 8fef24fcac682..4f9cfa032870a 100644 --- a/kernel/bpf/bpf_cgrp_storage.c +++ b/kernel/bpf/bpf_cgrp_storage.c @@ -11,29 +11,6 @@ DEFINE_BPF_STORAGE_CACHE(cgroup_cache); -static DEFINE_PER_CPU(int, bpf_cgrp_storage_busy); - -static void bpf_cgrp_storage_lock(void) -{ - cant_migrate(); - this_cpu_inc(bpf_cgrp_storage_busy); -} - -static void bpf_cgrp_storage_unlock(void) -{ - this_cpu_dec(bpf_cgrp_storage_busy); -} - -static bool bpf_cgrp_storage_trylock(void) -{ - cant_migrate(); - if (unlikely(this_cpu_inc_return(bpf_cgrp_storage_busy) != 1)) { - this_cpu_dec(bpf_cgrp_storage_busy); - return false; - } - return true; -} - static struct bpf_local_storage __rcu **cgroup_storage_ptr(void *owner) { struct cgroup *cg = owner; @@ -45,16 +22,14 @@ void bpf_cgrp_storage_free(struct cgroup *cgroup) { struct bpf_local_storage *local_storage; - rcu_read_lock_dont_migrate(); + rcu_read_lock(); local_storage = rcu_dereference(cgroup->bpf_cgrp_storage); if (!local_storage) goto out; - bpf_cgrp_storage_lock(); bpf_local_storage_destroy(local_storage); - bpf_cgrp_storage_unlock(); out: - rcu_read_unlock_migrate(); + rcu_read_unlock(); } static struct bpf_local_storage_data * @@ -83,9 +58,7 @@ static void *bpf_cgrp_storage_lookup_elem(struct bpf_map *map, void *key) if (IS_ERR(cgroup)) return ERR_CAST(cgroup); - bpf_cgrp_storage_lock(); sdata = cgroup_storage_lookup(cgroup, map, true); - bpf_cgrp_storage_unlock(); cgroup_put(cgroup); return sdata ? sdata->data : NULL; } @@ -102,10 +75,8 @@ static long bpf_cgrp_storage_update_elem(struct bpf_map *map, void *key, if (IS_ERR(cgroup)) return PTR_ERR(cgroup); - bpf_cgrp_storage_lock(); sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map, value, map_flags, false, GFP_ATOMIC); - bpf_cgrp_storage_unlock(); cgroup_put(cgroup); return PTR_ERR_OR_ZERO(sdata); } @@ -131,9 +102,7 @@ static long bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key) if (IS_ERR(cgroup)) return PTR_ERR(cgroup); - bpf_cgrp_storage_lock(); err = cgroup_storage_delete(cgroup, map); - bpf_cgrp_storage_unlock(); cgroup_put(cgroup); return err; } @@ -150,7 +119,7 @@ static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr) static void cgroup_storage_map_free(struct bpf_map *map) { - bpf_local_storage_map_free(map, &cgroup_cache, &bpf_cgrp_storage_busy); + bpf_local_storage_map_free(map, &cgroup_cache, NULL); } /* *gfp_flags* is a hidden argument provided by the verifier */ @@ -158,7 +127,6 @@ BPF_CALL_5(bpf_cgrp_storage_get, struct bpf_map *, map, struct cgroup *, cgroup, void *, value, u64, flags, gfp_t, gfp_flags) { struct bpf_local_storage_data *sdata; - bool nobusy; WARN_ON_ONCE(!bpf_rcu_lock_held()); if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE)) @@ -167,38 +135,27 @@ BPF_CALL_5(bpf_cgrp_storage_get, struct bpf_map *, map, struct cgroup *, cgroup, if (!cgroup) return (unsigned long)NULL; - nobusy = bpf_cgrp_storage_trylock(); - - sdata = cgroup_storage_lookup(cgroup, map, nobusy); + sdata = cgroup_storage_lookup(cgroup, map, NULL); if (sdata) - goto unlock; + goto out; /* only allocate new storage, when the cgroup is refcounted */ if (!percpu_ref_is_dying(&cgroup->self.refcnt) && - (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) && nobusy) + (flags & BPF_LOCAL_STORAGE_GET_F_CREATE)) sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map, value, BPF_NOEXIST, false, gfp_flags); -unlock: - if (nobusy) - bpf_cgrp_storage_unlock(); +out: return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : (unsigned long)sdata->data; } BPF_CALL_2(bpf_cgrp_storage_delete, struct bpf_map *, map, struct cgroup *, cgroup) { - int ret; - WARN_ON_ONCE(!bpf_rcu_lock_held()); if (!cgroup) return -EINVAL; - if (!bpf_cgrp_storage_trylock()) - return -EBUSY; - - ret = cgroup_storage_delete(cgroup, map); - bpf_cgrp_storage_unlock(); - return ret; + return cgroup_storage_delete(cgroup, map); } const struct bpf_map_ops cgrp_storage_map_ops = { From cb727fc6ffccc2c25fd9b8820ba15a294bdd7578 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:48 -0700 Subject: [PATCH 09/12] bpf: Remove unused percpu counter from bpf_local_storage_map_free Percpu locks have been removed from cgroup and task local storage. Now that all local storage no longer use percpu variables as locks preventing recursion, there is no need to pass them to bpf_local_storage_map_free(). Remove the argument from the function. Signed-off-by: Amery Hung --- include/linux/bpf_local_storage.h | 3 +-- kernel/bpf/bpf_cgrp_storage.c | 2 +- kernel/bpf/bpf_inode_storage.c | 2 +- kernel/bpf/bpf_local_storage.c | 7 +------ kernel/bpf/bpf_task_storage.c | 2 +- net/core/bpf_sk_storage.c | 2 +- 6 files changed, 6 insertions(+), 12 deletions(-) diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h index 2a0aae5168fa8..5888e012dfe37 100644 --- a/include/linux/bpf_local_storage.h +++ b/include/linux/bpf_local_storage.h @@ -170,8 +170,7 @@ bpf_local_storage_lookup(struct bpf_local_storage *local_storage, void bpf_local_storage_destroy(struct bpf_local_storage *local_storage); void bpf_local_storage_map_free(struct bpf_map *map, - struct bpf_local_storage_cache *cache, - int __percpu *busy_counter); + struct bpf_local_storage_cache *cache); int bpf_local_storage_map_check_btf(const struct bpf_map *map, const struct btf *btf, diff --git a/kernel/bpf/bpf_cgrp_storage.c b/kernel/bpf/bpf_cgrp_storage.c index 4f9cfa032870a..a57abb2956d55 100644 --- a/kernel/bpf/bpf_cgrp_storage.c +++ b/kernel/bpf/bpf_cgrp_storage.c @@ -119,7 +119,7 @@ static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr) static void cgroup_storage_map_free(struct bpf_map *map) { - bpf_local_storage_map_free(map, &cgroup_cache, NULL); + bpf_local_storage_map_free(map, &cgroup_cache); } /* *gfp_flags* is a hidden argument provided by the verifier */ diff --git a/kernel/bpf/bpf_inode_storage.c b/kernel/bpf/bpf_inode_storage.c index cedc99184dadd..470f4b02c79ea 100644 --- a/kernel/bpf/bpf_inode_storage.c +++ b/kernel/bpf/bpf_inode_storage.c @@ -184,7 +184,7 @@ static struct bpf_map *inode_storage_map_alloc(union bpf_attr *attr) static void inode_storage_map_free(struct bpf_map *map) { - bpf_local_storage_map_free(map, &inode_cache, NULL); + bpf_local_storage_map_free(map, &inode_cache); } const struct bpf_map_ops inode_storage_map_ops = { diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index 572956e2a72d1..3ce4dd7e7fc6f 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -917,8 +917,7 @@ bpf_local_storage_map_alloc(union bpf_attr *attr, } void bpf_local_storage_map_free(struct bpf_map *map, - struct bpf_local_storage_cache *cache, - int __percpu *busy_counter) + struct bpf_local_storage_cache *cache) { struct bpf_local_storage_map_bucket *b; struct bpf_local_storage_elem *selem; @@ -951,11 +950,7 @@ void bpf_local_storage_map_free(struct bpf_map *map, while ((selem = hlist_entry_safe( rcu_dereference_raw(hlist_first_rcu(&b->list)), struct bpf_local_storage_elem, map_node))) { - if (busy_counter) - this_cpu_inc(*busy_counter); while (bpf_selem_unlink(selem, true)); - if (busy_counter) - this_cpu_dec(*busy_counter); cond_resched_rcu(); } rcu_read_unlock(); diff --git a/kernel/bpf/bpf_task_storage.c b/kernel/bpf/bpf_task_storage.c index dd858226ada2d..4d53aebe67848 100644 --- a/kernel/bpf/bpf_task_storage.c +++ b/kernel/bpf/bpf_task_storage.c @@ -217,7 +217,7 @@ static struct bpf_map *task_storage_map_alloc(union bpf_attr *attr) static void task_storage_map_free(struct bpf_map *map) { - bpf_local_storage_map_free(map, &task_cache, NULL); + bpf_local_storage_map_free(map, &task_cache); } BTF_ID_LIST_GLOBAL_SINGLE(bpf_local_storage_map_btf_id, struct, bpf_local_storage_map) diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c index 7b3d44667ceec..7037b841cf119 100644 --- a/net/core/bpf_sk_storage.c +++ b/net/core/bpf_sk_storage.c @@ -62,7 +62,7 @@ void bpf_sk_storage_free(struct sock *sk) static void bpf_sk_storage_map_free(struct bpf_map *map) { - bpf_local_storage_map_free(map, &sk_cache, NULL); + bpf_local_storage_map_free(map, &sk_cache); } static struct bpf_map *bpf_sk_storage_map_alloc(union bpf_attr *attr) From cf8dd257a5f42f611c22628ed0cea693933a3536 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:49 -0700 Subject: [PATCH 10/12] selftests/bpf: Update task_local_storage/recursion test Update the expected result of the selftest as recursion of task local storage syscall and helpers have been relaxed. Now that the percpu counter is removed, task local storage helpers, bpf_task_storage_get() and bpf_task_storage_delete() can now run on the same CPU at the same time unless they cause deadlock. Note that since there is no percpu counter preventing recursion in task local storage helpers, bpf_trampoline now catches the recursion of on_update as reported by recursion_misses. on_enter: tp_btf/sys_enter on_update: fentry/bpf_local_storage_update Old behavior New behavior ____________ ____________ on_enter on_enter bpf_task_storage_get(&map_a) bpf_task_storage_get(&map_a) bpf_task_storage_trylock succeed bpf_local_storage_update(&map_a) bpf_local_storage_update(&map_a) on_update on_update bpf_task_storage_get(&map_a) bpf_task_storage_get(&map_a) bpf_task_storage_trylock fail on_update::misses++ (1) return NULL create and return map_a::ptr map_a::ptr += 1 (1) bpf_task_storage_delete(&map_a) return 0 bpf_task_storage_get(&map_b) bpf_task_storage_get(&map_b) bpf_task_storage_trylock fail on_update::misses++ (2) return NULL create and return map_b::ptr map_b::ptr += 1 (1) create and return map_a::ptr create and return map_a::ptr map_a::ptr = 200 map_a::ptr = 200 bpf_task_storage_get(&map_b) bpf_task_storage_get(&map_b) bpf_task_storage_trylock succeed lockless lookup succeed bpf_local_storage_update(&map_b) return map_b::ptr on_update bpf_task_storage_get(&map_a) bpf_task_storage_trylock fail lockless lookup succeed return map_a::ptr map_a::ptr += 1 (201) bpf_task_storage_delete(&map_a) bpf_task_storage_trylock fail return -EBUSY nr_del_errs++ (1) bpf_task_storage_get(&map_b) bpf_task_storage_trylock fail return NULL create and return ptr map_b::ptr = 100 Expected result: map_a::ptr = 201 map_a::ptr = 200 map_b::ptr = 100 map_b::ptr = 1 nr_del_err = 1 nr_del_err = 0 on_update::recursion_misses = 0 on_update::recursion_misses = 2 On_enter::recursion_misses = 0 on_enter::recursion_misses = 0 Signed-off-by: Amery Hung --- .../testing/selftests/bpf/prog_tests/task_local_storage.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c index 42e822ea352f1..559727b05e086 100644 --- a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c +++ b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c @@ -117,19 +117,19 @@ static void test_recursion(void) map_fd = bpf_map__fd(skel->maps.map_a); err = bpf_map_lookup_elem(map_fd, &task_fd, &value); ASSERT_OK(err, "lookup map_a"); - ASSERT_EQ(value, 201, "map_a value"); - ASSERT_EQ(skel->bss->nr_del_errs, 1, "bpf_task_storage_delete busy"); + ASSERT_EQ(value, 200, "map_a value"); + ASSERT_EQ(skel->bss->nr_del_errs, 0, "bpf_task_storage_delete busy"); map_fd = bpf_map__fd(skel->maps.map_b); err = bpf_map_lookup_elem(map_fd, &task_fd, &value); ASSERT_OK(err, "lookup map_b"); - ASSERT_EQ(value, 100, "map_b value"); + ASSERT_EQ(value, 1, "map_b value"); prog_fd = bpf_program__fd(skel->progs.on_update); memset(&info, 0, sizeof(info)); err = bpf_prog_get_info_by_fd(prog_fd, &info, &info_len); ASSERT_OK(err, "get prog info"); - ASSERT_EQ(info.recursion_misses, 0, "on_update prog recursion"); + ASSERT_EQ(info.recursion_misses, 2, "on_update prog recursion"); prog_fd = bpf_program__fd(skel->progs.on_enter); memset(&info, 0, sizeof(info)); From 0c190ef1334afd16deec2e4f9333565bdde3d1d0 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:50 -0700 Subject: [PATCH 11/12] selftests/bpf: Remove test_task_storage_map_stress_lookup Remove a test in test_maps that checks if the updating of the percpu counter in task local storage map is preemption safe as the percpu counter is now removed. Signed-off-by: Amery Hung --- .../bpf/map_tests/task_storage_map.c | 128 ------------------ .../bpf/progs/read_bpf_task_storage_busy.c | 38 ------ 2 files changed, 166 deletions(-) delete mode 100644 tools/testing/selftests/bpf/map_tests/task_storage_map.c delete mode 100644 tools/testing/selftests/bpf/progs/read_bpf_task_storage_busy.c diff --git a/tools/testing/selftests/bpf/map_tests/task_storage_map.c b/tools/testing/selftests/bpf/map_tests/task_storage_map.c deleted file mode 100644 index a4121d2248ac8..0000000000000 --- a/tools/testing/selftests/bpf/map_tests/task_storage_map.c +++ /dev/null @@ -1,128 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0 -/* Copyright (C) 2022. Huawei Technologies Co., Ltd */ -#define _GNU_SOURCE -#include -#include -#include -#include -#include -#include -#include - -#include -#include - -#include "bpf_util.h" -#include "test_maps.h" -#include "task_local_storage_helpers.h" -#include "read_bpf_task_storage_busy.skel.h" - -struct lookup_ctx { - bool start; - bool stop; - int pid_fd; - int map_fd; - int loop; -}; - -static void *lookup_fn(void *arg) -{ - struct lookup_ctx *ctx = arg; - long value; - int i = 0; - - while (!ctx->start) - usleep(1); - - while (!ctx->stop && i++ < ctx->loop) - bpf_map_lookup_elem(ctx->map_fd, &ctx->pid_fd, &value); - return NULL; -} - -static void abort_lookup(struct lookup_ctx *ctx, pthread_t *tids, unsigned int nr) -{ - unsigned int i; - - ctx->stop = true; - ctx->start = true; - for (i = 0; i < nr; i++) - pthread_join(tids[i], NULL); -} - -void test_task_storage_map_stress_lookup(void) -{ -#define MAX_NR_THREAD 4096 - unsigned int i, nr = 256, loop = 8192, cpu = 0; - struct read_bpf_task_storage_busy *skel; - pthread_t tids[MAX_NR_THREAD]; - struct lookup_ctx ctx; - cpu_set_t old, new; - const char *cfg; - int err; - - cfg = getenv("TASK_STORAGE_MAP_NR_THREAD"); - if (cfg) { - nr = atoi(cfg); - if (nr > MAX_NR_THREAD) - nr = MAX_NR_THREAD; - } - cfg = getenv("TASK_STORAGE_MAP_NR_LOOP"); - if (cfg) - loop = atoi(cfg); - cfg = getenv("TASK_STORAGE_MAP_PIN_CPU"); - if (cfg) - cpu = atoi(cfg); - - skel = read_bpf_task_storage_busy__open_and_load(); - err = libbpf_get_error(skel); - CHECK(err, "open_and_load", "error %d\n", err); - - /* Only for a fully preemptible kernel */ - if (!skel->kconfig->CONFIG_PREEMPTION) { - printf("%s SKIP (no CONFIG_PREEMPTION)\n", __func__); - read_bpf_task_storage_busy__destroy(skel); - skips++; - return; - } - - /* Save the old affinity setting */ - sched_getaffinity(getpid(), sizeof(old), &old); - - /* Pinned on a specific CPU */ - CPU_ZERO(&new); - CPU_SET(cpu, &new); - sched_setaffinity(getpid(), sizeof(new), &new); - - ctx.start = false; - ctx.stop = false; - ctx.pid_fd = sys_pidfd_open(getpid(), 0); - ctx.map_fd = bpf_map__fd(skel->maps.task); - ctx.loop = loop; - for (i = 0; i < nr; i++) { - err = pthread_create(&tids[i], NULL, lookup_fn, &ctx); - if (err) { - abort_lookup(&ctx, tids, i); - CHECK(err, "pthread_create", "error %d\n", err); - goto out; - } - } - - ctx.start = true; - for (i = 0; i < nr; i++) - pthread_join(tids[i], NULL); - - skel->bss->pid = getpid(); - err = read_bpf_task_storage_busy__attach(skel); - CHECK(err, "attach", "error %d\n", err); - - /* Trigger program */ - sys_gettid(); - skel->bss->pid = 0; - - CHECK(skel->bss->busy != 0, "bad bpf_task_storage_busy", "got %d\n", skel->bss->busy); -out: - read_bpf_task_storage_busy__destroy(skel); - /* Restore affinity setting */ - sched_setaffinity(getpid(), sizeof(old), &old); - printf("%s:PASS\n", __func__); -} diff --git a/tools/testing/selftests/bpf/progs/read_bpf_task_storage_busy.c b/tools/testing/selftests/bpf/progs/read_bpf_task_storage_busy.c deleted file mode 100644 index 69da05bb6c63e..0000000000000 --- a/tools/testing/selftests/bpf/progs/read_bpf_task_storage_busy.c +++ /dev/null @@ -1,38 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0 -/* Copyright (C) 2022. Huawei Technologies Co., Ltd */ -#include "vmlinux.h" -#include -#include - -extern bool CONFIG_PREEMPTION __kconfig __weak; -extern const int bpf_task_storage_busy __ksym; - -char _license[] SEC("license") = "GPL"; - -int pid = 0; -int busy = 0; - -struct { - __uint(type, BPF_MAP_TYPE_TASK_STORAGE); - __uint(map_flags, BPF_F_NO_PREALLOC); - __type(key, int); - __type(value, long); -} task SEC(".maps"); - -SEC("raw_tp/sys_enter") -int BPF_PROG(read_bpf_task_storage_busy) -{ - int *value; - - if (!CONFIG_PREEMPTION) - return 0; - - if (bpf_get_current_pid_tgid() >> 32 != pid) - return 0; - - value = bpf_this_cpu_ptr(&bpf_task_storage_busy); - if (value) - busy = *value; - - return 0; -} From ea0876a15d090ecf05c38555486ab59b5f81ec53 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Thu, 2 Oct 2025 15:53:51 -0700 Subject: [PATCH 12/12] selftests/bpf: Choose another percpu variable in bpf for btf_dump test bpf_cgrp_storage_busy has been removed. Use bpf_bprintf_nest_level instead. This percpu variable is also in the bpf subsystem so that if it is removed in the future, BPF-CI will catch this type of CI- breaking change. Signed-off-by: Amery Hung --- tools/testing/selftests/bpf/prog_tests/btf_dump.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/btf_dump.c b/tools/testing/selftests/bpf/prog_tests/btf_dump.c index 10cba526d3e63..f1642794f70ed 100644 --- a/tools/testing/selftests/bpf/prog_tests/btf_dump.c +++ b/tools/testing/selftests/bpf/prog_tests/btf_dump.c @@ -875,8 +875,8 @@ static void test_btf_dump_var_data(struct btf *btf, struct btf_dump *d, TEST_BTF_DUMP_VAR(btf, d, NULL, str, "cpu_number", int, BTF_F_COMPACT, "int cpu_number = (int)100", 100); #endif - TEST_BTF_DUMP_VAR(btf, d, NULL, str, "bpf_cgrp_storage_busy", int, BTF_F_COMPACT, - "static int bpf_cgrp_storage_busy = (int)2", 2); + TEST_BTF_DUMP_VAR(btf, d, NULL, str, "bpf_bprintf_nest_level", int, BTF_F_COMPACT, + "static int bpf_bprintf_nest_level = (int)2", 2); } struct btf_dump_string_ctx {