From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757358Ab3FCMgm (ORCPT ); Mon, 3 Jun 2013 08:36:42 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:21412 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755566Ab3FCMgk (ORCPT ); Mon, 3 Jun 2013 08:36:40 -0400 Date: Mon, 3 Jun 2013 08:36:34 -0400 From: Konrad Rzeszutek Wilk To: Akinobu Mita Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH] frontswap: fix incorrect zeroing and allocation size for frontswap_map Message-ID: <20130603123634.GE6893@phenom.dumpdata.com> References: <1370130777-6707-1-git-send-email-akinobu.mita@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1370130777-6707-1-git-send-email-akinobu.mita@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 02, 2013 at 08:52:57AM +0900, Akinobu Mita wrote: > The bitmap accessed by bitops must have enough size to hold the required > numbers of bits rounded up to a multiple of BITS_PER_LONG. And the bitmap > must not be zeroed by memset() if the number of bits cleared is not > a multiple of BITS_PER_LONG. > > This fixes incorrect zeroing and allocation size for frontswap_map. > The incorrect zeroing part doesn't cause any problem because > frontswap_map is freed just after zeroing. But the wrongly calculated > allocation size may cause the problem. > > For 32bit systems, the allocation size of frontswap_map is about twice as > large as required size. For 64bit systems, the allocation size is smaller > than requeired if the number of bits is not a multiple of BITS_PER_LONG. ^^^^^^^^^ required. Looks OK to me. Thanks for catching this. I will test it out and if it does not break any regression tests should go for the next rc. Thanks! > > Signed-off-by: Akinobu Mita > Cc: Konrad Rzeszutek Wilk > --- > mm/frontswap.c | 2 +- > mm/swapfile.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/frontswap.c b/mm/frontswap.c > index 538367e..1b24bdc 100644 > --- a/mm/frontswap.c > +++ b/mm/frontswap.c > @@ -319,7 +319,7 @@ void __frontswap_invalidate_area(unsigned type) > return; > frontswap_ops->invalidate_area(type); > atomic_set(&sis->frontswap_pages, 0); > - memset(sis->frontswap_map, 0, sis->max / sizeof(long)); > + bitmap_zero(sis->frontswap_map, sis->max); > } > clear_bit(type, need_init); > } > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 6c340d9..746af55b 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -2116,7 +2116,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > } > /* frontswap enabled? set up bit-per-page map for frontswap */ > if (frontswap_enabled) > - frontswap_map = vzalloc(maxpages / sizeof(long)); > + frontswap_map = vzalloc(BITS_TO_LONGS(maxpages) * sizeof(long)); > > if (p->bdev) { > if (blk_queue_nonrot(bdev_get_queue(p->bdev))) { > -- > 1.8.1.4 >