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Message-ID: <4713EC5B.7050000@goop.org>
Date: Mon, 15 Oct 2007 15:40:27 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Matt Mackall <mpm@...enic.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org, Dave Hansen <haveblue@...ibm.com>,
Rusty Russell <rusty@...tcorp.com.au>,
David Rientjes <rientjes@...gle.com>,
Fengguang Wu <wfg@...l.ustc.edu.cn>
Subject: Re: [PATCH 4/11] maps3: introduce a generic page walker
Matt Mackall wrote:
> Introduce a general page table walker
>
Definitely approve in principle, but some comments:
> Signed-off-by: Matt Mackall <mpm@...enic.com>
>
> 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 <linux/mm.h>
> +#include <linux/highmem.h>
> +#include <linux/sched.h>
> +
> +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)? Is the second addr
argument for the address range being mapped by this thing? Why pass
addr twice?
> + if (err)
> + break;
> + } while (pte++, addr += PAGE_SIZE, addr != end);
> +
> + pte_unmap(pte);
> + return err;
> +}
> +
> +static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
> + struct mm_walk *walk, void *private)
> +{
> + pmd_t *pmd;
> + unsigned long next;
> + int err = 0;
> +
> + pmd = pmd_offset(pud, addr);
> + do {
> + next = pmd_addr_end(addr, end);
> + if (pmd_none_or_clear_bad(pmd)) {
> + if (walk->pte_hole)
> + err = walk->pte_hole(addr, next, private);
> + if (err)
> + break;
> + continue;
> + }
> + if (walk->pmd_entry)
> + err = walk->pmd_entry(pmd, addr, next, private);
> + if (!err && walk->pte_entry)
> + err = walk_pte_range(pmd, addr, next, walk, private);
> + if (err)
> + break;
> + } while (pmd++, addr = next, addr != end);
> +
> + return err;
> +}
> +
> +static int walk_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end,
> + struct mm_walk *walk, void *private)
> +{
> + pud_t *pud;
> + unsigned long next;
> + int err = 0;
> +
> + pud = pud_offset(pgd, addr);
> + do {
> + next = pud_addr_end(addr, end);
> + if (pud_none_or_clear_bad(pud)) {
> + if (walk->pte_hole)
> + err = walk->pte_hole(addr, next, private);
> + if (err)
> + break;
> + continue;
> + }
> + if (walk->pud_entry)
> + err = walk->pud_entry(pud, addr, next, private);
> + if (!err && (walk->pmd_entry || walk->pte_entry))
> + err = walk_pmd_range(pud, addr, next, walk, private);
> + if (err)
> + break;
> + } while (pud++, addr = next, addr != end);
> +
> + return err;
> +}
> +
> +/*
> + * 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.
> + */
> +int walk_page_range(struct mm_struct *mm,
> + unsigned long addr, unsigned long end,
> + struct mm_walk *walk, void *private)
> +{
> + pgd_t *pgd;
> + unsigned long next;
> + int err = 0;
> +
> + if (addr >= end)
> + return err;
> +
> + pgd = pgd_offset(mm, addr);
> + do {
> + next = pgd_addr_end(addr, end);
> + if (pgd_none_or_clear_bad(pgd)) {
> + if (walk->pte_hole)
> + err = walk->pte_hole(addr, next, private);
> + if (err)
> + break;
> + continue;
> + }
> + if (walk->pgd_entry)
> + err = walk->pgd_entry(pgd, addr, next, private);
> + if (!err &&
> + (walk->pud_entry || walk->pmd_entry || walk->pte_entry))
> + err = walk_pud_range(pgd, addr, next, walk, private);
> + if (err)
> + return err;
> + } while (pgd++, addr = next, addr != end);
> +
> + return err;
> +}
>
-
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