From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot0-f199.google.com (mail-ot0-f199.google.com [74.125.82.199]) by kanga.kvack.org (Postfix) with ESMTP id DC4A66B02B4 for ; Fri, 9 Jun 2017 17:23:52 -0400 (EDT) Received: by mail-ot0-f199.google.com with SMTP id 3so19723185otz.1 for ; Fri, 09 Jun 2017 14:23:52 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id w184sor722311oif.14.2017.06.09.14.23.51 for (Google Transport Security); Fri, 09 Jun 2017 14:23:52 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20170607204859.13104-1-ross.zwisler@linux.intel.com> References: <20170607204859.13104-1-ross.zwisler@linux.intel.com> From: Dan Williams Date: Fri, 9 Jun 2017 14:23:51 -0700 Message-ID: Subject: Re: [PATCH 1/3] mm: add vm_insert_mixed_mkwrite() Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Ross Zwisler Cc: Andrew Morton , Linux Kernel Mailing List , linux-xfs@vger.kernel.org, Theodore Ts'o , Matthew Wilcox , "Darrick J. Wong" , Jonathan Corbet , Steven Rostedt , linux-doc@vger.kernel.org, linux-mm , Dave Hansen , Ingo Molnar , Andreas Dilger , Alexander Viro , linux-fsdevel , Jan Kara , ext4 hackers , Christoph Hellwig , "linux-nvdimm@lists.01.org" On Wed, Jun 7, 2017 at 1:48 PM, Ross Zwisler wrote: > To be able to use the common 4k zero page in DAX we need to have our PTE > fault path look more like our PMD fault path where a PTE entry can be > marked as dirty and writeable as it is first inserted, rather than waiting > for a follow-up dax_pfn_mkwrite() => finish_mkwrite_fault() call. > > Right now we can rely on having a dax_pfn_mkwrite() call because we can > distinguish between these two cases in do_wp_page(): > > case 1: 4k zero page => writable DAX storage > case 2: read-only DAX storage => writeable DAX storage > > This distinction is made by via vm_normal_page(). vm_normal_page() returns > false for the common 4k zero page, though, just as it does for DAX ptes. > Instead of special casing the DAX + 4k zero page case, we will simplify our > DAX PTE page fault sequence so that it matches our DAX PMD sequence, and > get rid of dax_pfn_mkwrite() completely. > > This means that insert_pfn() needs to follow the lead of insert_pfn_pmd() > and allow us to pass in a 'mkwrite' flag. If 'mkwrite' is set insert_pfn() > will do the work that was previously done by wp_page_reuse() as part of the > dax_pfn_mkwrite() call path. > > Signed-off-by: Ross Zwisler > --- > include/linux/mm.h | 9 +++++++-- > mm/memory.c | 21 ++++++++++++++------- > 2 files changed, 21 insertions(+), 9 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index b892e95..11e323a 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -2294,10 +2294,15 @@ int vm_insert_pfn(struct vm_area_struct *vma, unsigned long addr, > unsigned long pfn); > int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr, > unsigned long pfn, pgprot_t pgprot); > -int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr, > - pfn_t pfn); > +int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr, > + pfn_t pfn, bool mkwrite); Are there any other planned public users of vm_insert_mixed_mkwrite() that would pass false? I think not. > int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len); > > +static inline int vm_insert_mixed(struct vm_area_struct *vma, > + unsigned long addr, pfn_t pfn) > +{ > + return vm_insert_mixed_mkwrite(vma, addr, pfn, false); > +} ...in other words instead of making the distinction of vm_insert_mixed_mkwrite() and vm_insert_mixed() with extra flag argument just move the distinction into mm/memory.c directly. So, the prototype remains the same as vm_insert_mixed() int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr, pfn_t pfn); ...and only static insert_pfn(...) needs to change. -- 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