From: Amery Hung <ameryhung@gmail.com> mainline inclusion from mainline-v7.0-rc1 commit 1b7e0cae85accc9e728004511193e995cd040300 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9180 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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. Remove the selem_linked_to_map_lockless() check as an selem in the common paths (not bpf_local_storage_map_free() or bpf_local_storage_destroy()), will be unlinked under b->lock and local_storage->lock and therefore no other threads can unlink the selem from map at the same time. In bpf_local_storage_destroy(), ignore the return of bpf_selem_unlink_map() for now. A later patch will allow bpf_local_storage_destroy() to unlink selems even when failing to acquire locks. Note that while this patch removes all callers of selem_linked_to_map(), a later patch that introduces bpf_selem_unlink_nofail() will use it again. 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/20260205222916.1788211-3-ameryhung@gmail.com Conflicts: kernel/bpf/bpf_local_storage.c [remove selem_linked_to_map as it not use] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/bpf_local_storage.c | 62 +++++++++++++++++++++------------- 1 file changed, 39 insertions(+), 23 deletions(-) diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index 934a1426b6f2..26ce2bff3b36 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -61,16 +61,6 @@ static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem) return !hlist_unhashed(&selem->snode); } -static bool selem_linked_to_map_lockless(const struct bpf_local_storage_elem *selem) -{ - return !hlist_unhashed_lockless(&selem->map_node); -} - -static bool selem_linked_to_map(const struct bpf_local_storage_elem *selem) -{ - return !hlist_unhashed(&selem->map_node); -} - struct bpf_local_storage_elem * bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner, void *value, bool charge_mem, gfp_t gfp_flags) @@ -374,25 +364,27 @@ 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; struct bpf_local_storage_map_bucket *b; unsigned long flags; - if (unlikely(!selem_linked_to_map_lockless(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, local_storage); raw_spin_lock_irqsave(&b->lock, flags); - if (likely(selem_linked_to_map(selem))) - hlist_del_init_rcu(&selem->map_node); + 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) +{ + hlist_del_init_rcu(&selem->map_node); } void bpf_selem_link_map(struct bpf_local_storage_map *smap, @@ -409,13 +401,24 @@ 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_bucket *b, + struct bpf_local_storage_elem *selem) +{ + 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); } @@ -483,6 +486,8 @@ 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)); @@ -509,7 +514,10 @@ int bpf_local_storage_alloc(void *owner, storage->owner = owner; bpf_selem_link_storage_nolock(storage, first_selem); - bpf_selem_link_map(smap, storage, first_selem); + + b = select_bucket(smap, storage); + raw_spin_lock_irqsave(&b->lock, flags); + bpf_selem_link_map_nolock(b, first_selem); owner_storage_ptr = (struct bpf_local_storage **)owner_storage(smap, owner); @@ -525,7 +533,8 @@ 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; @@ -539,6 +548,7 @@ int bpf_local_storage_alloc(void *owner, * bucket->list under rcu_read_lock(). */ } + raw_spin_unlock_irqrestore(&b->lock, flags); return 0; @@ -560,7 +570,8 @@ 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; - unsigned long flags; + struct bpf_local_storage_map_bucket *b; + unsigned long flags, b_flags; int err; /* BPF_EXIST and BPF_NOEXIST cannot be both set */ @@ -644,20 +655,25 @@ 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, local_storage, selem); + bpf_selem_link_map_nolock(b, selem); /* 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, false); } + raw_spin_unlock_irqrestore(&b->lock, b_flags); unlock: raw_spin_unlock_irqrestore(&local_storage->lock, flags); if (alloc_selem) { -- 2.34.1