From patchwork Wed Mar 8 06:59:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Martin KaFai Lau X-Patchwork-Id: 13165287 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D56CCC64EC4 for ; Wed, 8 Mar 2023 07:00:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229785AbjCHHAP (ORCPT ); Wed, 8 Mar 2023 02:00:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47536 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229778AbjCHHAO (ORCPT ); Wed, 8 Mar 2023 02:00:14 -0500 Received: from out-1.mta1.migadu.com (out-1.mta1.migadu.com [95.215.58.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2A965A2187 for ; Tue, 7 Mar 2023 23:00:12 -0800 (PST) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1678258810; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=JVe6utBeIutvVLM54TwKK0HEzILqqxuiZtyABUd00lo=; b=NvdBKDvzzhI3h88J+YWzcDbmuu6X8TAFLSr5KAbDLxgEh1osPV4qWFiKvn7Ff0Db/3NbHt eJmrHX51jaFyUltQx83IZWIcdUmE6hNoosQk10jB7Ek8o2/aP3hJ6fiEcg8b8xtETXjkel MXrH4A2udU5I1rjJprYL4B+U7dq4Rp4= From: Martin KaFai Lau To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@meta.com, Kumar Kartikeya Dwivedi Subject: [PATCH v2 bpf-next 07/17] bpf: Remove bpf_selem_free_fields*_rcu Date: Tue, 7 Mar 2023 22:59:26 -0800 Message-Id: <20230308065936.1550103-8-martin.lau@linux.dev> In-Reply-To: <20230308065936.1550103-1-martin.lau@linux.dev> References: <20230308065936.1550103-1-martin.lau@linux.dev> MIME-Version: 1.0 X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net From: Martin KaFai Lau This patch removes the bpf_selem_free_fields*_rcu. The bpf_obj_free_fields() can be done before the call_rcu_trasks_trace() and kfree_rcu(). It is needed when a later patch uses bpf_mem_cache_alloc/free. In bpf hashtab, bpf_obj_free_fields() is also called before calling bpf_mem_cache_free. The discussion can be found in https://lore.kernel.org/bpf/f67021ee-21d9-bfae-6134-4ca542fab843@linux.dev/ Acked-by: Kumar Kartikeya Dwivedi Signed-off-by: Martin KaFai Lau --- kernel/bpf/bpf_local_storage.c | 67 +++------------------------------- 1 file changed, 5 insertions(+), 62 deletions(-) diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c index 70c34a948c3c..715deaaefe13 100644 --- a/kernel/bpf/bpf_local_storage.c +++ b/kernel/bpf/bpf_local_storage.c @@ -109,27 +109,6 @@ static void bpf_local_storage_free_rcu(struct rcu_head *rcu) kfree_rcu(local_storage, rcu); } -static void bpf_selem_free_fields_rcu(struct rcu_head *rcu) -{ - struct bpf_local_storage_elem *selem; - struct bpf_local_storage_map *smap; - - selem = container_of(rcu, struct bpf_local_storage_elem, rcu); - /* protected by the rcu_barrier*() */ - smap = rcu_dereference_protected(SDATA(selem)->smap, true); - bpf_obj_free_fields(smap->map.record, SDATA(selem)->data); - kfree(selem); -} - -static void bpf_selem_free_fields_trace_rcu(struct rcu_head *rcu) -{ - /* Free directly if Tasks Trace RCU GP also implies RCU GP */ - if (rcu_trace_implies_rcu_gp()) - bpf_selem_free_fields_rcu(rcu); - else - call_rcu(rcu, bpf_selem_free_fields_rcu); -} - static void bpf_selem_free_trace_rcu(struct rcu_head *rcu) { struct bpf_local_storage_elem *selem; @@ -151,7 +130,6 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor { struct bpf_local_storage_map *smap; bool free_local_storage; - struct btf_record *rec; void *owner; smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held()); @@ -192,26 +170,11 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor SDATA(selem)) RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL); - /* A different RCU callback is chosen whenever we need to free - * additional fields in selem data before freeing selem. - * bpf_local_storage_map_free only executes rcu_barrier to wait for RCU - * callbacks when it has special fields, hence we can only conditionally - * dereference smap, as by this time the map might have already been - * freed without waiting for our call_rcu callback if it did not have - * any special fields. - */ - rec = smap->map.record; - if (!reuse_now) { - if (!IS_ERR_OR_NULL(rec)) - call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_fields_trace_rcu); - else - call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_trace_rcu); - } else { - if (!IS_ERR_OR_NULL(rec)) - call_rcu(&selem->rcu, bpf_selem_free_fields_rcu); - else - kfree_rcu(selem, rcu); - } + bpf_obj_free_fields(smap->map.record, SDATA(selem)->data); + if (!reuse_now) + call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_trace_rcu); + else + kfree_rcu(selem, rcu); if (rcu_access_pointer(local_storage->smap) == smap) RCU_INIT_POINTER(local_storage->smap, NULL); @@ -769,26 +732,6 @@ void bpf_local_storage_map_free(struct bpf_map *map, */ synchronize_rcu(); - /* Only delay freeing of smap, buckets are not needed anymore */ kvfree(smap->buckets); - - /* When local storage has special fields, callbacks for - * bpf_selem_free_fields_rcu and bpf_selem_free_fields_trace_rcu will - * keep using the map BTF record, we need to execute an RCU barrier to - * wait for them as the record will be freed right after our map_free - * callback. - */ - if (!IS_ERR_OR_NULL(smap->map.record)) { - rcu_barrier_tasks_trace(); - /* We cannot skip rcu_barrier() when rcu_trace_implies_rcu_gp() - * is true, because while call_rcu invocation is skipped in that - * case in bpf_selem_free_fields_trace_rcu (and all local - * storage maps pass reuse_now = false), there can be - * call_rcu callbacks based on reuse_now = true in the - * while ((selem = ...)) loop above or when owner's free path - * calls bpf_local_storage_unlink_nolock. - */ - rcu_barrier(); - } bpf_map_area_free(smap); }