From patchwork Tue Sep 5 15:46:49 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oleg Nesterov X-Patchwork-Id: 13374527 X-Patchwork-Delegate: bpf@iogearbox.net Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4494E2571 for ; Tue, 5 Sep 2023 15:47:45 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2CEC6E6 for ; Tue, 5 Sep 2023 08:47:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1693928863; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to; bh=0ZAYlH739l+imp77wdMvEIGsmJrTe5vS2BECbqXhogw=; b=TCfNDXHKw28J+DVbML+6S20LKtw8QyfM+AB9ZsR/YLYWr3hZJ1egKuFGQkbYwaKMlD4Gm+ DvlGXZ19GEwEtGpbDOtRgj2zXvbVB1mGIf4IRuFjXHPWFB9B3fcH8zVEstUhajF5lcl1ie 60v9U7+rbL6VM0wL0Lm+7Qsj+hGuY9I= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-538-0z7dQYXuOei6eh2sUN9d2Q-1; Tue, 05 Sep 2023 11:47:41 -0400 X-MC-Unique: 0z7dQYXuOei6eh2sUN9d2Q-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4CDCA1C09A4D; Tue, 5 Sep 2023 15:47:41 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.45.226.87]) by smtp.corp.redhat.com (Postfix) with SMTP id 11C15C03291; Tue, 5 Sep 2023 15:47:39 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 5 Sep 2023 17:46:50 +0200 (CEST) Date: Tue, 5 Sep 2023 17:46:49 +0200 From: Oleg Nesterov To: Yonghong Song Cc: "Eric W. Biederman" , Kui-Feng Lee , bpf@vger.kernel.org Subject: [PATCH bpf-next v2 2/5] bpf: task_group_seq_get_next: cleanup the usage of get/put_task_struct Message-ID: <20230905154649.GA24935@redhat.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230905154612.GA24872@redhat.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: bpf@iogearbox.net get_pid_task() makes no sense, the code does put_task_struct() soon after. Use find_task_by_pid_ns() instead of find_pid_ns + get_pid_task and kill put_task_struct(), this allows to do get_task_struct() only once before return. While at it, kill the unnecessary "if (!pid)" check in the "if (!*tid)" block, this matches the next usage of find_pid_ns() + get_pid_task() in this function. Signed-off-by: Oleg Nesterov Acked-by: Yonghong Song --- kernel/bpf/task_iter.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 4d1125108014..1589ec3faded 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -42,9 +42,6 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm if (!*tid) { /* The first time, the iterator calls this function. */ pid = find_pid_ns(common->pid, common->ns); - if (!pid) - return NULL; - task = get_pid_task(pid, PIDTYPE_TGID); if (!task) return NULL; @@ -66,17 +63,12 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm return task; } - pid = find_pid_ns(common->pid_visiting, common->ns); - if (!pid) - return NULL; - - task = get_pid_task(pid, PIDTYPE_PID); + task = find_task_by_pid_ns(common->pid_visiting, common->ns); if (!task) return NULL; retry: next_task = next_thread(task); - put_task_struct(task); saved_tid = *tid; *tid = __task_pid_nr_ns(next_task, PIDTYPE_PID, common->ns); @@ -88,7 +80,6 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm return NULL; } - get_task_struct(next_task); common->pid_visiting = *tid; if (skip_if_dup_files && task->files == task->group_leader->files) { @@ -96,6 +87,7 @@ static struct task_struct *task_group_seq_get_next(struct bpf_iter_seq_task_comm goto retry; } + get_task_struct(next_task); return next_task; }