RE: Kill off hugepage_vma()
From: Chen, Kenneth W
Date: Fri Apr 16 2004 - 17:22:35 EST
Original post on LKML:
http://www.ussg.iu.edu/hypermail/linux/kernel/0404.2/0017.html
>>>> David Gibson wrote on Thursday, April 15, 2004 11:22 PM
> Kenneth, does the patch below look reasonable? It's close to trivial
> on everything except IA64, which I can't easily test on. Actually, it
> occurs to me that this may even fix a bug on IA64 - if follow_page()
> was called on an address in region 1 that wasn't in a VMA, then I
> think it would attempt to follow it as a normal page, which sounds
> bad.
Thanks to well written code in the caller of follow_page(), that they
always call find_extend_vma() to make sure address belongs to a vma
before calling down to follow_page(). So there is no bug here.
Minor FYI: on ia64, huge page address is in region 4.
> hugepage_vma() is both misleadingly named and unnecessary. On most
> archs it always returns NULL, and on IA64 the vma it returns is never
> used. The function's real purpose is to determine whether the address
> it is passed is a special hugepage address which must be looked up in
> hugepage pagetables, rather than being looked up in the normal
> pagetables (which might have specially marked hugepage PMDs or PTEs).
One way or the other, the check has to be there. If the name is vague,
a new name can be proposed.
> This patch kills off hugepage_vma() and folds the logic it really
> needs into follow_huge_addr(). That now returns a (page *) if called
> on a special hugepage address, and an error encoded with ERR_PTR
> otherwise. This also requires tweaking the IA64 code to check that
> the hugepage PTE is present in follow_huge_addr() - previously this
> was guaranteed, since it was only called if the address was in an
> existing hugepage VMA, and hugepages are always prefaulted.
Why not do one step further? Instead of call a dummy function that
always return false, why not stub it out in the header file for arch
that don't need follow_huge_addr? This would speedup everyone.
I propose the following patch:
diff -Nur linux-2.6.5/arch/i386/mm/hugetlbpage.c linux-2.6.5.htlb/arch/i386/mm/hugetlbpage.c
--- linux-2.6.5/arch/i386/mm/hugetlbpage.c 2004-04-16 13:23:22.000000000 -0700
+++ linux-2.6.5.htlb/arch/i386/mm/hugetlbpage.c 2004-04-16 14:15:28.000000000 -0700
@@ -182,18 +182,6 @@
#else
-struct page *
-follow_huge_addr(struct mm_struct *mm,
- struct vm_area_struct *vma, unsigned long address, int write)
-{
- return NULL;
-}
-
-struct vm_area_struct *hugepage_vma(struct mm_struct *mm, unsigned long addr)
-{
- return NULL;
-}
-
int pmd_huge(pmd_t pmd)
{
return !!(pmd_val(pmd) & _PAGE_PSE);
diff -Nur linux-2.6.5/arch/ia64/mm/hugetlbpage.c linux-2.6.5.htlb/arch/ia64/mm/hugetlbpage.c
--- linux-2.6.5/arch/ia64/mm/hugetlbpage.c 2004-04-16 13:23:22.000000000 -0700
+++ linux-2.6.5.htlb/arch/ia64/mm/hugetlbpage.c 2004-04-16 14:20:35.000000000 -0700
@@ -149,19 +149,7 @@
return i;
}
-struct vm_area_struct *hugepage_vma(struct mm_struct *mm, unsigned long addr)
-{
- if (mm->used_hugetlb) {
- if (REGION_NUMBER(addr) == REGION_HPAGE) {
- struct vm_area_struct *vma = find_vma(mm, addr);
- if (vma && is_vm_hugetlb_page(vma))
- return vma;
- }
- }
- return NULL;
-}
-
-struct page *follow_huge_addr(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long addr, int write)
+struct page *follow_huge_addr(struct mm_struct *mm, unsigned long addr, int write)
{
struct page *page;
pte_t *ptep;
diff -Nur linux-2.6.5/arch/ppc64/mm/hugetlbpage.c linux-2.6.5.htlb/arch/ppc64/mm/hugetlbpage.c
--- linux-2.6.5/arch/ppc64/mm/hugetlbpage.c 2004-04-16 13:23:22.000000000 -0700
+++ linux-2.6.5.htlb/arch/ppc64/mm/hugetlbpage.c 2004-04-16 14:37:19.000000000 -0700
@@ -334,18 +334,6 @@
return i;
}
-struct page *
-follow_huge_addr(struct mm_struct *mm,
- struct vm_area_struct *vma, unsigned long address, int write)
-{
- return NULL;
-}
-
-struct vm_area_struct *hugepage_vma(struct mm_struct *mm, unsigned long addr)
-{
- return NULL;
-}
-
int pmd_huge(pmd_t pmd)
{
return pmd_hugepage(pmd);
diff -Nur linux-2.6.5/arch/sh/mm/hugetlbpage.c linux-2.6.5.htlb/arch/sh/mm/hugetlbpage.c
--- linux-2.6.5/arch/sh/mm/hugetlbpage.c 2004-04-16 13:23:22.000000000 -0700
+++ linux-2.6.5.htlb/arch/sh/mm/hugetlbpage.c 2004-04-16 14:16:09.000000000 -0700
@@ -165,18 +165,6 @@
return i;
}
-struct page *follow_huge_addr(struct mm_struct *mm,
- struct vm_area_struct *vma,
- unsigned long address, int write)
-{
- return NULL;
-}
-
-struct vm_area_struct *hugepage_vma(struct mm_struct *mm, unsigned long addr)
-{
- return NULL;
-}
-
int pmd_huge(pmd_t pmd)
{
return 0;
diff -Nur linux-2.6.5/arch/sparc64/mm/hugetlbpage.c linux-2.6.5.htlb/arch/sparc64/mm/hugetlbpage.c
--- linux-2.6.5/arch/sparc64/mm/hugetlbpage.c 2004-04-16 13:23:22.000000000 -0700
+++ linux-2.6.5.htlb/arch/sparc64/mm/hugetlbpage.c 2004-04-16 14:16:24.000000000 -0700
@@ -162,18 +162,6 @@
return i;
}
-struct page *follow_huge_addr(struct mm_struct *mm,
- struct vm_area_struct *vma,
- unsigned long address, int write)
-{
- return NULL;
-}
-
-struct vm_area_struct *hugepage_vma(struct mm_struct *mm, unsigned long addr)
-{
- return NULL;
-}
-
int pmd_huge(pmd_t pmd)
{
return 0;
diff -Nur linux-2.6.5/include/asm-ia64/page.h linux-2.6.5.htlb/include/asm-ia64/page.h
--- linux-2.6.5/include/asm-ia64/page.h 2004-04-03 19:36:19.000000000 -0800
+++ linux-2.6.5.htlb/include/asm-ia64/page.h 2004-04-16 14:07:52.000000000 -0700
@@ -47,6 +47,7 @@
# define HAVE_ARCH_HUGETLB_UNMAPPED_AREA
# define ARCH_HAS_HUGEPAGE_ONLY_RANGE
+# define ARCH_HAS_FOLLOW_HUGE_ADDR
#endif /* CONFIG_HUGETLB_PAGE */
#ifdef __ASSEMBLY__
@@ -123,6 +124,7 @@
# define is_hugepage_only_range(addr, len) \
(REGION_NUMBER(addr) == REGION_HPAGE && \
REGION_NUMBER((addr)+(len)) == REGION_HPAGE)
+# define prepare_follow_huge_addr(addr) (REGION_NUMBER(addr) == REGION_HPAGE)
extern unsigned int hpage_shift;
#endif
diff -Nur linux-2.6.5/include/linux/hugetlb.h linux-2.6.5.htlb/include/linux/hugetlb.h
--- linux-2.6.5/include/linux/hugetlb.h 2004-04-16 13:23:25.000000000 -0700
+++ linux-2.6.5.htlb/include/linux/hugetlb.h 2004-04-16 14:14:16.000000000 -0700
@@ -22,10 +22,6 @@
int hugetlb_report_meminfo(char *);
int is_hugepage_mem_enough(size_t);
unsigned long hugetlb_total_pages(void);
-struct page *follow_huge_addr(struct mm_struct *mm, struct vm_area_struct *vma,
- unsigned long address, int write);
-struct vm_area_struct *hugepage_vma(struct mm_struct *mm,
- unsigned long address);
struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
pmd_t *pmd, int write);
int is_aligned_hugepage_range(unsigned long addr, unsigned long len);
@@ -55,6 +51,13 @@
int prepare_hugepage_range(unsigned long addr, unsigned long len);
#endif
+#ifndef ARCH_HAS_FOLLOW_HUGE_ADDR
+#define prepare_follow_huge_addr(addr) 0
+#define follow_huge_addr(mm, addr, write) 0
+#else
+struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, int write);
+#endif
+
#else /* !CONFIG_HUGETLB_PAGE */
static inline int is_vm_hugetlb_page(struct vm_area_struct *vma)
@@ -67,7 +70,8 @@
}
#define follow_hugetlb_page(m,v,p,vs,a,b,i) ({ BUG(); 0; })
-#define follow_huge_addr(mm, vma, addr, write) 0
+#define prepare_follow_huge_addr(addr) 0
+#define follow_huge_addr(mm, addr, write) 0
#define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; })
#define hugetlb_prefault(mapping, vma) ({ BUG(); 0; })
#define zap_hugepage_range(vma, start, len) BUG()
@@ -75,7 +79,6 @@
#define huge_page_release(page) BUG()
#define is_hugepage_mem_enough(size) 0
#define hugetlb_report_meminfo(buf) 0
-#define hugepage_vma(mm, addr) 0
#define mark_mm_hugetlb(mm, vma) do { } while (0)
#define follow_huge_pmd(mm, addr, pmd, write) 0
#define is_aligned_hugepage_range(addr, len) 0
diff -Nur linux-2.6.5/mm/memory.c linux-2.6.5.htlb/mm/memory.c
--- linux-2.6.5/mm/memory.c 2004-04-16 13:23:25.000000000 -0700
+++ linux-2.6.5.htlb/mm/memory.c 2004-04-16 14:20:49.000000000 -0700
@@ -629,11 +629,9 @@
pmd_t *pmd;
pte_t *ptep, pte;
unsigned long pfn;
- struct vm_area_struct *vma;
- vma = hugepage_vma(mm, address);
- if (vma)
- return follow_huge_addr(mm, vma, address, write);
+ if (prepare_follow_huge_addr(address))
+ return follow_huge_addr(mm, address, write);
pgd = pgd_offset(mm, address);
if (pgd_none(*pgd) || pgd_bad(*pgd))
-
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