From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 0A81D6B0038 for ; Mon, 9 Jan 2017 14:49:02 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id b1so1777657264pgc.5 for ; Mon, 09 Jan 2017 11:49:02 -0800 (PST) Received: from shards.monkeyblade.net (shards.monkeyblade.net. [184.105.139.130]) by mx.google.com with ESMTP id s11si89622927pgc.259.2017.01.09.11.49.00 for ; Mon, 09 Jan 2017 11:49:01 -0800 (PST) Date: Mon, 09 Jan 2017 14:48:59 -0500 (EST) Message-Id: <20170109.144859.1717139396935735509.davem@davemloft.net> Subject: Re: Crash in -next due to 'mm/vmalloc: replace opencoded 4-level page walkers' From: David Miller In-Reply-To: <20170109113707.GQ19067@nuc-i3427.alporthouse.com> References: <20161028171825.GA15116@roeck-us.net> <20170109113707.GQ19067@nuc-i3427.alporthouse.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: chris@chris-wilson.co.uk Cc: linux@roeck-us.net, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, sparclinux@vger.kernel.org, linux-mm@kvack.org From: Chris Wilson Date: Mon, 9 Jan 2017 11:37:07 +0000 > Could some mm expert explain why it is safe for mm/vmalloc.c to ignore > huge pud/pmd that raise BUG_ON in the same code in mm/memory.c > (vmap_pmd_range() vs apply_to_pmd_range())? > > At a guess, is sparc64 covering the init_mm with a huge zero page? How > is it then meant to be split? Something like We map the linear physical area (PAGE_OFFSET --> PAGE_OFFSET + max_phys_addr) using huge pages unless DEBUG_PAGEALLOC is enabled. It is not meant to be split, and that's why we don't use huge pages when DEBUG_PAGEALLOC is set since that requires changes to the mapping to be possible. -- 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