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Fri, 24 Apr 2026 12:51:07 -0700 (PDT) Received: from localhost ([2a03:2880:30ff::]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a4185bc1f6sm6115972e87.20.2026.04.24.12.51.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 24 Apr 2026 12:51:05 -0700 (PDT) From: Mykyta Yatsenko Date: Fri, 24 Apr 2026 12:50:45 -0700 Subject: [PATCH bpf-next v3 03/10] bpf: Implement get_next_key() resizable hashtab Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260424-rhash-v3-3-d0fa0ce4379b@meta.com> References: <20260424-rhash-v3-0-d0fa0ce4379b@meta.com> In-Reply-To: <20260424-rhash-v3-0-d0fa0ce4379b@meta.com> To: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kafai@meta.com, kernel-team@meta.com, eddyz87@gmail.com, memxor@gmail.com, herbert@gondor.apana.org.au Cc: Mykyta Yatsenko , Emil Tsalapatis X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1777060253; l=2077; i=yatsenko@meta.com; s=20260324; h=from:subject:message-id; bh=oWKflP+3EMNnYhPaeM1Y3Qi7Qeu2b3fhkY5i3pmk2co=; b=VstBuowceQq9OgPLbXmgb+3/JUlm3rS63pgv72/ogdcKcd6QFX5oqLAjvtg/ET7x8upXD4b51 rm7FvH3Z4IVANOGpYdCtdXQ+HB/Sd4utzNUFr+jWx1pvHSff8w3VBXH X-Developer-Key: i=yatsenko@meta.com; a=ed25519; pk=1zCUBXUa66KmzfjNsG8YNlMj2ckPdqBPvFq2ww3/YaA= From: Mykyta Yatsenko Implement rhtab_map_get_next_key() for the BPF resizable hashtable. Called from syscall, so it's safe to use rhashtable walk API that uses spinlocks internally. Signed-off-by: Mykyta Yatsenko Reviewed-by: Emil Tsalapatis --- kernel/bpf/hashtab.c | 43 ++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index a37bd2a7b30f..d37f3d548d36 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -3014,13 +3014,54 @@ static int rhtab_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf) return insn - insn_buf; } +/* Helper to get next element, handling -EAGAIN during resize */ +static struct rhtab_elem *rhtab_iter_next(struct rhashtable_iter *iter) +{ + struct rhtab_elem *elem; + + while ((elem = rhashtable_walk_next(iter))) { + if (IS_ERR(elem)) { + if (PTR_ERR(elem) == -EAGAIN) + continue; + return NULL; + } + return elem; + } + + return NULL; +} + static void rhtab_map_free_internal_structs(struct bpf_map *map) { } static int rhtab_map_get_next_key(struct bpf_map *map, void *key, void *next_key) { - return -EOPNOTSUPP; + struct bpf_rhtab *rhtab = container_of(map, struct bpf_rhtab, map); + struct rhashtable_iter iter; + struct rhtab_elem *elem; + int ret = -ENOENT; + + /* + * Hold RCU across enter_from + walk_start to prevent the + * element cached by enter_from from being freed before + * walk_start re-acquires RCU. + */ + guard(rcu)(); + /* If key is not found, places iterator at the beginning */ + rhashtable_walk_enter_from(&rhtab->ht, &iter, key, rhtab->params); + rhashtable_walk_start(&iter); + + elem = rhtab_iter_next(&iter); + if (elem) { + memcpy(next_key, elem->data, map->key_size); + ret = 0; + } + + rhashtable_walk_stop(&iter); + rhashtable_walk_exit(&iter); + + return ret; } static void rhtab_map_seq_show_elem(struct bpf_map *map, void *key, struct seq_file *m) -- 2.52.0