From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932558AbcH2Uyg (ORCPT ); Mon, 29 Aug 2016 16:54:36 -0400 Received: from mail-oi0-f42.google.com ([209.85.218.42]:34044 "EHLO mail-oi0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755524AbcH2Uyf (ORCPT ); Mon, 29 Aug 2016 16:54:35 -0400 MIME-Version: 1.0 In-Reply-To: <1472503455.1532.28.camel@hpe.com> References: <1472497881-9323-1-git-send-email-toshi.kani@hpe.com> <1472497881-9323-2-git-send-email-toshi.kani@hpe.com> <1472503455.1532.28.camel@hpe.com> From: Dan Williams Date: Mon, 29 Aug 2016 13:54:33 -0700 Message-ID: Subject: Re: [PATCH v4 RESEND 1/2] thp, dax: add thp_get_unmapped_area for pmd mappings To: "Kani, Toshimitsu" Cc: "kirill.shutemov@linux.intel.com" , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "adilger.kernel@dilger.ca" , "mike.kravetz@oracle.com" , "mawilcox@microsoft.com" , "akpm@linux-foundation.org" , "linux-nvdimm@lists.01.org" , "linux-fsdevel@vger.kernel.org" , "ross.zwisler@linux.intel.com" , "tytso@mit.edu" , "david@fromorbit.com" , "jack@suse.cz" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 29, 2016 at 1:44 PM, Kani, Toshimitsu wrote: > On Mon, 2016-08-29 at 12:34 -0700, Dan Williams wrote: >> On Mon, Aug 29, 2016 at 12:11 PM, Toshi Kani >> wrote: >> > >> > When CONFIG_FS_DAX_PMD is set, DAX supports mmap() using pmd page >> > size. This feature relies on both mmap virtual address and FS >> > block (i.e. physical address) to be aligned by the pmd page size. >> > Users can use mkfs options to specify FS to align block >> > allocations. However, aligning mmap address requires code changes >> > to existing applications for providing a pmd-aligned address to >> > mmap(). >> > >> > For instance, fio with "ioengine=mmap" performs I/Os with mmap() >> > [1]. It calls mmap() with a NULL address, which needs to be changed >> > to provide a pmd-aligned address for testing with DAX pmd mappings. >> > Changing all applications that call mmap() with NULL is >> > undesirable. >> > >> > Add thp_get_unmapped_area(), which can be called by filesystem's >> > get_unmapped_area to align an mmap address by the pmd size for >> > a DAX file. It calls the default handler, mm->get_unmapped_area(), >> > to find a range and then aligns it for a DAX file. >> > >> > The patch is based on Matthew Wilcox's change that allows adding >> > support of the pud page size easily. > : >> >> Reviewed-by: Dan Williams > > Great! > >> ...with one minor nit: >> >> >> > >> > include/linux/huge_mm.h | 7 +++++++ >> > mm/huge_memory.c | 43 >> > +++++++++++++++++++++++++++++++++++++++++++ >> > 2 files changed, 50 insertions(+) >> > >> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >> > index 6f14de4..4fca526 100644 >> > --- a/include/linux/huge_mm.h >> > +++ b/include/linux/huge_mm.h >> > @@ -87,6 +87,10 @@ extern bool is_vma_temporary_stack(struct >> > vm_area_struct *vma); >> > >> > extern unsigned long transparent_hugepage_flags; >> > >> > +extern unsigned long thp_get_unmapped_area(struct file *filp, >> > + unsigned long addr, unsigned long len, unsigned >> > long pgoff, >> > + unsigned long flags); >> > + >> > extern void prep_transhuge_page(struct page *page); >> > extern void free_transhuge_page(struct page *page); >> > >> > @@ -169,6 +173,9 @@ void put_huge_zero_page(void); >> > static inline void prep_transhuge_page(struct page *page) {} >> > >> > #define transparent_hugepage_flags 0UL >> > + >> > +#define thp_get_unmapped_area NULL >> >> Lets make this: >> >> static inline unsigned long thp_get_unmapped_area(struct file *filp, >> unsigned long addr, unsigned long len, unsigned long >> pgoff, >> unsigned long flags) >> { >> return 0; >> } >> >> ...to get some type checking in the CONFIG_TRANSPARENT_HUGEPAGE=n >> case. >> > > Per get_unmapped_area() in mm/mmap.c, I think we need to set it to NULL > when we do not override current->mm->get_unmapped_area. Ah, ok.