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 2FC19C433FE for ; Fri, 11 Mar 2022 23:33:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229622AbiCKXey (ORCPT ); Fri, 11 Mar 2022 18:34:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39196 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229616AbiCKXex (ORCPT ); Fri, 11 Mar 2022 18:34:53 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B5F1D17F6B0; Fri, 11 Mar 2022 15:33:47 -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 dfw.source.kernel.org (Postfix) with ESMTPS id BD48160EED; Fri, 11 Mar 2022 23:33:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A910C340E9; Fri, 11 Mar 2022 23:33:45 +0000 (UTC) Date: Fri, 11 Mar 2022 18:33:43 -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: <20220311183343.4d8c94a5@gandalf.local.home> In-Reply-To: <20220311223028.1865-1-beaub@linux.microsoft.com> References: <20220311223028.1865-1-beaub@linux.microsoft.com> 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 14:30:28 -0800 Beau Belgrave wrote: > diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c > index 2b5e9fdb63a0..59c900789757 100644 > --- a/kernel/trace/trace_events_user.c > +++ b/kernel/trace/trace_events_user.c > @@ -1587,16 +1587,20 @@ static void set_page_reservations(bool set) > static int __init trace_events_user_init(void) > { > int ret; > + struct page *register_pages; The int ret should come last. > > /* 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); > + register_pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, > + get_order(MAX_EVENTS)); > > - if (!register_page_data) > + if (!register_pages) > return -ENOMEM; > > + register_page_data = page_address(register_pages); > + > set_page_reservations(true); > > ret = create_user_tracefs(); > @@ -1604,7 +1608,7 @@ 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(register_pages, get_order(MAX_EVENTS)); > return ret; > } > 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. -- Steve diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c index 4febc1d6ae72..6941d0794347 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. */ @@ -1606,41 +1607,25 @@ static int create_user_tracefs(void) return -ENODEV; } -static void set_page_reservations(bool set) -{ - int page; - - for (page = 0; page < MAX_PAGES; ++page) { - void *addr = register_page_data + (PAGE_SIZE * page); - - if (set) - SetPageReserved(virt_to_page(addr)); - else - ClearPageReserved(virt_to_page(addr)); - } -} - 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; - - set_page_reservations(true); + register_page_data = page_address(pages); ret = create_user_tracefs(); if (ret) { pr_warn("user_events could not register with tracefs\n"); - set_page_reservations(false); - kfree(register_page_data); + free_page((unsigned long)register_page_data); return ret; }