From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx181.postini.com [74.125.245.181]) by kanga.kvack.org (Postfix) with SMTP id 5C9566B0068 for ; Mon, 30 Jan 2012 12:16:04 -0500 (EST) Received: by iadk27 with SMTP id k27so7884686iad.14 for ; Mon, 30 Jan 2012 09:16:03 -0800 (PST) Date: Mon, 30 Jan 2012 09:15:58 -0800 From: Tejun Heo Subject: Re: [PATCH 1/3] percpu: use ZERO_SIZE_PTR / ZERO_OR_NULL_PTR Message-ID: <20120130171558.GB3355@google.com> References: <1327912654-8738-1-git-send-email-dmitry.antipov@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1327912654-8738-1-git-send-email-dmitry.antipov@linaro.org> Sender: owner-linux-mm@kvack.org List-ID: To: Dmitry Antipov Cc: Christoph Lameter , Rusty Russell , linux-mm@kvack.org, linux-kernel@vger.kernel.org, patches@linaro.org, linaro-dev@lists.linaro.org On Mon, Jan 30, 2012 at 12:37:34PM +0400, Dmitry Antipov wrote: > Fix pcpu_alloc() to return ZERO_SIZE_PTR if requested size is 0; > fix free_percpu() to check passed pointer with ZERO_OR_NULL_PTR. > > Signed-off-by: Dmitry Antipov > --- > mm/percpu.c | 16 +++++++++++----- > 1 files changed, 11 insertions(+), 5 deletions(-) > > diff --git a/mm/percpu.c b/mm/percpu.c > index f47af91..e903a19 100644 > --- a/mm/percpu.c > +++ b/mm/percpu.c > @@ -702,7 +702,8 @@ static struct pcpu_chunk *pcpu_chunk_addr_search(void *addr) > * Does GFP_KERNEL allocation. > * > * RETURNS: > - * Percpu pointer to the allocated area on success, NULL on failure. > + * ZERO_SIZE_PTR if @size is zero, percpu pointer to the > + * allocated area on success or NULL on failure. > */ > static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved) > { > @@ -713,7 +714,10 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved) > unsigned long flags; > void __percpu *ptr; > > - if (unlikely(!size || size > PCPU_MIN_UNIT_SIZE || align > PAGE_SIZE)) { > + if (unlikely(!size)) > + return ZERO_SIZE_PTR; Percpu pointers are in a different address space and using ZERO_SIZE_PTR directly will trigger sparse address space warning. Also, I'm not entirely sure whether 16 is guaranteed to be unused in percpu address space (maybe it is but I don't think we have anything enforcing that). Thanks. -- tejun -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org