From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id A45816B0071 for ; Sun, 21 Nov 2010 22:06:43 -0500 (EST) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id oAM36d7A016678 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Mon, 22 Nov 2010 12:06:39 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id DCDBA45DE51 for ; Mon, 22 Nov 2010 12:06:38 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id B1E4C45DE4E for ; Mon, 22 Nov 2010 12:06:38 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 9A7FEE08001 for ; Mon, 22 Nov 2010 12:06:38 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 572301DB803A for ; Mon, 22 Nov 2010 12:06:38 +0900 (JST) Date: Mon, 22 Nov 2010 12:01:02 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [BUGFIX][PATCH] pagemap: set pagemap walk limit to PMD boundary Message-Id: <20101122120102.e0e76373.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <1290157665-17215-1-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1290157665-17215-1-git-send-email-n-horiguchi@ah.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Naoya Horiguchi Cc: LKML , linux-mm , Andrew Morton , Jun'ichi Nomura , Matt Mackall List-ID: On Fri, 19 Nov 2010 18:07:45 +0900 Naoya Horiguchi wrote: > Currently one pagemap_read() call walks in PAGEMAP_WALK_SIZE bytes > (== 512 pages.) But there is a corner case where walk_pmd_range() > accidentally runs over a VMA associated with a hugetlbfs file. > > For example, when a process has mappings to VMAs as shown below: > > # cat /proc//maps > ... > 3a58f6d000-3a58f72000 rw-p 00000000 00:00 0 > 7fbd51853000-7fbd51855000 rw-p 00000000 00:00 0 > 7fbd5186c000-7fbd5186e000 rw-p 00000000 00:00 0 > 7fbd51a00000-7fbd51c00000 rw-s 00000000 00:12 8614 /hugepages/test > > then pagemap_read() goes into walk_pmd_range() path and walks in the range > 0x7fbd51853000-0x7fbd51a53000, but the hugetlbfs VMA should be handled > by walk_hugetlb_range(). Otherwise PMD for the hugepage is considered bad > and cleared, which causes undesirable results. > > This patch fixes it by separating pagemap walk range into one PMD. > > Signed-off-by: Naoya Horiguchi > Cc: Andrew Morton > Cc: Jun'ichi Nomura > Cc: KAMEZAWA Hiroyuki > Cc: Matt Mackall > --- > fs/proc/task_mmu.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index da6b01d..c126c83 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -706,6 +706,7 @@ static int pagemap_hugetlb_range(pte_t *pte, unsigned long hmask, > * skip over unmapped regions. > */ > #define PAGEMAP_WALK_SIZE (PMD_SIZE) > +#define PAGEMAP_WALK_MASK (PMD_MASK) > static ssize_t pagemap_read(struct file *file, char __user *buf, > size_t count, loff_t *ppos) > { > @@ -776,7 +777,7 @@ static ssize_t pagemap_read(struct file *file, char __user *buf, > unsigned long end; > > pm.pos = 0; > - end = start_vaddr + PAGEMAP_WALK_SIZE; > + end = (start_vaddr + PAGEMAP_WALK_SIZE) & PAGEMAP_WALK_MASK; > /* overflow ? */ > if (end < start_vaddr || end > end_vaddr) > end = end_vaddr; Ack. But ALIGN() can't be used ? Thanks, -Kame -- 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org