From mboxrd@z Thu Jan 1 00:00:00 1970 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 56456C433EF for ; Fri, 11 Mar 2022 23:44:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229652AbiCKXpu (ORCPT ); Fri, 11 Mar 2022 18:45:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43802 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229762AbiCKXpt (ORCPT ); Fri, 11 Mar 2022 18:45:49 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 70F8D9FC5; Fri, 11 Mar 2022 15:44:45 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id EDAA0B80EDF; Fri, 11 Mar 2022 23:44:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4FD0C340E9; Fri, 11 Mar 2022 23:44:41 +0000 (UTC) Date: Fri, 11 Mar 2022 18:44:40 -0500 From: Steven Rostedt To: Beau Belgrave Cc: mhiramat@kernel.org, anders.roxell@linaro.org, linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-next@vger.kernel.org Subject: Re: [PATCH] user_events: Use alloc_pages instead of kzalloc for register pages Message-ID: <20220311184440.537e9f83@gandalf.local.home> In-Reply-To: <20220311183343.4d8c94a5@gandalf.local.home> References: <20220311223028.1865-1-beaub@linux.microsoft.com> <20220311183343.4d8c94a5@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On Fri, 11 Mar 2022 18:33:43 -0500 Steven Rostedt wrote: > I tried it slightly differently. Why waist bits if MAX_EVENTS is greater > than the order. That is, make MAX_EVENTS depend on the order, not the other > way around. Here's a version that keeps the reserving part as well as some bug fixes (I didn't even compile the previous version ;-) -- Steve diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c index 4febc1d6ae72..e10ad057e797 100644 --- a/kernel/trace/trace_events_user.c +++ b/kernel/trace/trace_events_user.c @@ -30,9 +30,10 @@ /* * Limits how many trace_event calls user processes can create: - * Must be multiple of PAGE_SIZE. + * Must be a power of two of PAGE_SIZE. */ -#define MAX_PAGES 1 +#define MAX_PAGE_ORDER 0 +#define MAX_PAGES (1 << MAX_PAGE_ORDER) #define MAX_EVENTS (MAX_PAGES * PAGE_SIZE) /* Limit how long of an event name plus args within the subsystem. */ @@ -1622,16 +1623,17 @@ static void set_page_reservations(bool set) static int __init trace_events_user_init(void) { + struct page *pages; int ret; /* Zero all bits beside 0 (which is reserved for failures) */ bitmap_zero(page_bitmap, MAX_EVENTS); set_bit(0, page_bitmap); - register_page_data = kzalloc(MAX_EVENTS, GFP_KERNEL); - - if (!register_page_data) + pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, MAX_PAGE_ORDER); + if (!pages) return -ENOMEM; + register_page_data = page_address(pages); set_page_reservations(true); @@ -1640,7 +1642,7 @@ static int __init trace_events_user_init(void) if (ret) { pr_warn("user_events could not register with tracefs\n"); set_page_reservations(false); - kfree(register_page_data); + __free_pages(pages, MAX_PAGE_ORDER); return ret; }