From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752718Ab2GJCfo (ORCPT ); Mon, 9 Jul 2012 22:35:44 -0400 Received: from LGEMRELSE7Q.lge.com ([156.147.1.151]:64344 "EHLO LGEMRELSE7Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752010Ab2GJCfm (ORCPT ); Mon, 9 Jul 2012 22:35:42 -0400 X-AuditID: 9c930197-b7b49ae0000027b8-b7-4ffb94fb65cc Message-ID: <4FFB94FF.8030401@kernel.org> Date: Tue, 10 Jul 2012 11:35:43 +0900 From: Minchan Kim User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 MIME-Version: 1.0 To: Seth Jennings CC: Greg Kroah-Hartman , Andrew Morton , Dan Magenheimer , Konrad Rzeszutek Wilk , Nitin Gupta , Robert Jennings , linux-mm@kvack.org, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/4] zsmalloc: add details to zs_map_object boiler plate References: <1341263752-10210-1-git-send-email-sjenning@linux.vnet.ibm.com> <1341263752-10210-4-git-send-email-sjenning@linux.vnet.ibm.com> In-Reply-To: <1341263752-10210-4-git-send-email-sjenning@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/03/2012 06:15 AM, Seth Jennings wrote: > Add information on the usage limits of zs_map_object() > > Signed-off-by: Seth Jennings > --- > drivers/staging/zsmalloc/zsmalloc-main.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c > index 4942d41..abf7c13 100644 > --- a/drivers/staging/zsmalloc/zsmalloc-main.c > +++ b/drivers/staging/zsmalloc/zsmalloc-main.c > @@ -747,7 +747,12 @@ EXPORT_SYMBOL_GPL(zs_free); > * > * Before using an object allocated from zs_malloc, it must be mapped using > * this function. When done with the object, it must be unmapped using > - * zs_unmap_object > + * zs_unmap_object. > + * > + * Only one object can be mapped per cpu at a time. There is no protection > + * against nested mappings. > + * > + * This function returns with preemption and page faults disabled. > */ > void *zs_map_object(struct zs_pool *pool, unsigned long handle) > { > The comment is good but I hope we can detect it automatically with DEBUG option. It wouldn't be hard but it's a debug patch so not critical until we receive some report about the bug. The possibility for nesting is that it is used by irq context. A uses the mapping . . . IRQ happen B uses the mapping in IRQ context . . . Maybe we need local_irq_save/restore in zs_[un]map_object path. -- Kind regards, Minchan Kim From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx129.postini.com [74.125.245.129]) by kanga.kvack.org (Postfix) with SMTP id A82336B0069 for ; Mon, 9 Jul 2012 22:35:42 -0400 (EDT) Message-ID: <4FFB94FF.8030401@kernel.org> Date: Tue, 10 Jul 2012 11:35:43 +0900 From: Minchan Kim MIME-Version: 1.0 Subject: Re: [PATCH 3/4] zsmalloc: add details to zs_map_object boiler plate References: <1341263752-10210-1-git-send-email-sjenning@linux.vnet.ibm.com> <1341263752-10210-4-git-send-email-sjenning@linux.vnet.ibm.com> In-Reply-To: <1341263752-10210-4-git-send-email-sjenning@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Seth Jennings Cc: Greg Kroah-Hartman , Andrew Morton , Dan Magenheimer , Konrad Rzeszutek Wilk , Nitin Gupta , Robert Jennings , linux-mm@kvack.org, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org On 07/03/2012 06:15 AM, Seth Jennings wrote: > Add information on the usage limits of zs_map_object() > > Signed-off-by: Seth Jennings > --- > drivers/staging/zsmalloc/zsmalloc-main.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c > index 4942d41..abf7c13 100644 > --- a/drivers/staging/zsmalloc/zsmalloc-main.c > +++ b/drivers/staging/zsmalloc/zsmalloc-main.c > @@ -747,7 +747,12 @@ EXPORT_SYMBOL_GPL(zs_free); > * > * Before using an object allocated from zs_malloc, it must be mapped using > * this function. When done with the object, it must be unmapped using > - * zs_unmap_object > + * zs_unmap_object. > + * > + * Only one object can be mapped per cpu at a time. There is no protection > + * against nested mappings. > + * > + * This function returns with preemption and page faults disabled. > */ > void *zs_map_object(struct zs_pool *pool, unsigned long handle) > { > The comment is good but I hope we can detect it automatically with DEBUG option. It wouldn't be hard but it's a debug patch so not critical until we receive some report about the bug. The possibility for nesting is that it is used by irq context. A uses the mapping . . . IRQ happen B uses the mapping in IRQ context . . . Maybe we need local_irq_save/restore in zs_[un]map_object path. -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org