From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761735AbXJOXc0 (ORCPT ); Mon, 15 Oct 2007 19:32:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752973AbXJOXcQ (ORCPT ); Mon, 15 Oct 2007 19:32:16 -0400 Received: from waste.org ([66.93.16.53]:59981 "EHLO waste.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754840AbXJOXcP (ORCPT ); Mon, 15 Oct 2007 19:32:15 -0400 Date: Mon, 15 Oct 2007 18:30:46 -0500 From: Matt Mackall To: Jeremy Fitzhardinge Cc: Andrew Morton , linux-kernel@vger.kernel.org, Dave Hansen , Rusty Russell , David Rientjes , Fengguang Wu Subject: Re: [PATCH 4/11] maps3: introduce a generic page walker Message-ID: <20071015233046.GY19691@waste.org> References: <5.290135367@selenic.com> <4713EC5B.7050000@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4713EC5B.7050000@goop.org> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 15, 2007 at 03:40:27PM -0700, Jeremy Fitzhardinge wrote: > Matt Mackall wrote: > > Introduce a general page table walker > > > > Definitely approve in principle, but some comments: > > > Signed-off-by: Matt Mackall > > > > Index: l/include/linux/mm.h > > =================================================================== > > --- l.orig/include/linux/mm.h 2007-10-09 17:37:59.000000000 -0500 > > +++ l/include/linux/mm.h 2007-10-10 11:46:37.000000000 -0500 > > @@ -773,6 +773,17 @@ unsigned long unmap_vmas(struct mmu_gath > > struct vm_area_struct *start_vma, unsigned long start_addr, > > unsigned long end_addr, unsigned long *nr_accounted, > > struct zap_details *); > > + > > +struct mm_walk { > > + int (*pgd_entry)(pgd_t *, unsigned long, unsigned long, void *); > > + int (*pud_entry)(pud_t *, unsigned long, unsigned long, void *); > > + int (*pmd_entry)(pmd_t *, unsigned long, unsigned long, void *); > > + int (*pte_entry)(pte_t *, unsigned long, unsigned long, void *); > > + int (*pte_hole) (unsigned long, unsigned long, void *); > > +}; > > > > It would be nice to have some clue about when each of these functions > are called (depth first? pre or post order?), and what their params > are. Does it call a callback for folded pagetable levels? > > Can pte_hole be used to create new mappings while we're traversing the > pagetable? Apparently not, because it continues after calling it. > > > + > > +int walk_page_range(struct mm_struct *, unsigned long addr, unsigned long end, > > + struct mm_walk *walk, void *private); > > void free_pgd_range(struct mmu_gather **tlb, unsigned long addr, > > unsigned long end, unsigned long floor, unsigned long ceiling); > > void free_pgtables(struct mmu_gather **tlb, struct vm_area_struct *start_vma, > > Index: l/mm/Makefile > > =================================================================== > > --- l.orig/mm/Makefile 2007-10-09 17:37:59.000000000 -0500 > > +++ l/mm/Makefile 2007-10-10 11:46:37.000000000 -0500 > > @@ -5,7 +5,7 @@ > > mmu-y := nommu.o > > mmu-$(CONFIG_MMU) := fremap.o highmem.o madvise.o memory.o mincore.o \ > > mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \ > > - vmalloc.o > > + vmalloc.o pagewalk.o > > > > obj-y := bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \ > > page_alloc.o page-writeback.o pdflush.o \ > > Index: l/mm/pagewalk.c > > =================================================================== > > --- /dev/null 1970-01-01 00:00:00.000000000 +0000 > > +++ l/mm/pagewalk.c 2007-10-10 11:46:37.000000000 -0500 > > @@ -0,0 +1,120 @@ > > +#include > > +#include > > +#include > > + > > +static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > > + struct mm_walk *walk, void *private) > > +{ > > + pte_t *pte; > > + int err = 0; > > + > > + pte = pte_offset_map(pmd, addr); > > + do { > > + err = walk->pte_entry(pte, addr, addr, private); > > > > Should this be (pte, addr, addr+PAGE_SIZE, private)? Probably - the pattern is [start, end). Either that or we should have one arg. > > +/* > > + * walk_page_range - walk a memory map's page tables with a callback > > + * @mm - memory map to walk > > + * @addr - starting address > > + * @end - ending address > > + * @walk - set of callbacks to invoke for each level of the tree > > + * @private - private data passed to the callback function > > + * > > + * Recursively walk the page table for the memory area in a VMA, calling > > + * a callback for every bottom-level (PTE) page table. > > > > It calls a callback for every level of the pagetable. Oops. -- Mathematics is the supreme nostalgia of our time.