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Re: hugepage patches
1/4
Using a futex in a large page causes a kernel lockup in __pin_page() -
because __pin_page's page revalidation uses follow_page(), and follow_page()
doesn't work for hugepages.
The patch fixes up follow_page() to return the appropriate 4k page for
hugepages.
This incurs a vma lookup for each follow_page(), which is considerable
overhead in some situations. We only _need_ to do this if the architecture
cannot determin a page's hugeness from the contents of the PMD.
So this patch is a "reference" implementation for, say, PPC BAT-based
hugepages.
arch/i386/mm/hugetlbpage.c | 29 +++++++++++++++++++++++++++++
include/linux/hugetlb.h | 18 ++++++++++++++++--
include/linux/sched.h | 4 +++-
mm/memory.c | 5 +++++
mm/mmap.c | 2 +-
linux/mm.h | 0
6 files changed, 54 insertions(+), 4 deletions(-)
diff -puN mm/memory.c~pin_page-fix mm/memory.c
--- 25/mm/memory.c~pin_page-fix Fri Jan 31 13:32:13 2003
+++ 25-akpm/mm/memory.c Fri Jan 31 14:29:59 2003
@@ -607,6 +607,11 @@ follow_page(struct mm_struct *mm, unsign
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);
pgd = pgd_offset(mm, address);
if (pgd_none(*pgd) || pgd_bad(*pgd))
diff -puN include/linux/hugetlb.h~pin_page-fix include/linux/hugetlb.h
--- 25/include/linux/hugetlb.h~pin_page-fix Fri Jan 31 13:32:13 2003
+++ 25-akpm/include/linux/hugetlb.h Fri Jan 31 14:29:59 2003
@@ -20,16 +20,28 @@ int hugetlb_prefault(struct address_spac
void huge_page_release(struct page *);
int hugetlb_report_meminfo(char *);
int is_hugepage_mem_enough(size_t);
-
+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);
extern int htlbpage_max;
+static inline void
+mark_mm_hugetlb(struct mm_struct *mm, struct vm_area_struct *vma)
+{
+ if (is_vm_hugetlb_page(vma))
+ mm->used_hugetlb = 1;
+}
+
#else /* !CONFIG_HUGETLB_PAGE */
+
static inline int is_vm_hugetlb_page(struct vm_area_struct *vma)
{
return 0;
}
-#define follow_hugetlb_page(m,v,p,vs,a,b,i) ({ BUG(); 0; })
+#define follow_hugetlb_page(m,v,p,vs,a,b,i) ({ BUG(); 0; })
+#define follow_huge_addr(mm, vma, 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()
@@ -37,6 +49,8 @@ static inline int is_vm_hugetlb_page(str
#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)
#endif /* !CONFIG_HUGETLB_PAGE */
diff -puN arch/i386/mm/hugetlbpage.c~pin_page-fix arch/i386/mm/hugetlbpage.c
--- 25/arch/i386/mm/hugetlbpage.c~pin_page-fix Fri Jan 31 13:32:13 2003
+++ 25-akpm/arch/i386/mm/hugetlbpage.c Fri Jan 31 14:29:59 2003
@@ -150,6 +150,35 @@ back1:
return i;
}
+struct page *
+follow_huge_addr(struct mm_struct *mm,
+ struct vm_area_struct *vma, unsigned long address, int write)
+{
+ unsigned long start = address;
+ int length = 1;
+ int nr;
+ struct page *page;
+
+ nr = follow_hugetlb_page(mm, vma, &page, NULL, &start, &length, 0);
+ if (nr == 1)
+ return page;
+ return NULL;
+}
+
+/*
+ * If virtual address `addr' lies within a huge page, return its controlling
+ * VMA, else NULL.
+ */
+struct vm_area_struct *hugepage_vma(struct mm_struct *mm, unsigned long addr)
+{
+ if (mm->used_hugetlb) {
+ struct vm_area_struct *vma = find_vma(mm, addr);
+ if (vma && is_vm_hugetlb_page(vma))
+ return vma;
+ }
+ return NULL;
+}
+
void free_huge_page(struct page *page)
{
BUG_ON(page_count(page));
diff -puN mm/mmap.c~pin_page-fix mm/mmap.c
--- 25/mm/mmap.c~pin_page-fix Fri Jan 31 13:32:13 2003
+++ 25-akpm/mm/mmap.c Fri Jan 31 13:32:13 2003
@@ -362,6 +362,7 @@ static void vma_link(struct mm_struct *m
if (mapping)
up(&mapping->i_shared_sem);
+ mark_mm_hugetlb(mm, vma);
mm->map_count++;
validate_mm(mm);
}
@@ -1427,7 +1428,6 @@ void exit_mmap(struct mm_struct *mm)
kmem_cache_free(vm_area_cachep, vma);
vma = next;
}
-
}
/* Insert vm structure into process list sorted by address
diff -puN include/linux/mm.h~pin_page-fix include/linux/mm.h
diff -puN include/linux/sched.h~pin_page-fix include/linux/sched.h
--- 25/include/linux/sched.h~pin_page-fix Fri Jan 31 13:32:13 2003
+++ 25-akpm/include/linux/sched.h Fri Jan 31 13:32:13 2003
@@ -203,7 +203,9 @@ struct mm_struct {
unsigned long swap_address;
unsigned dumpable:1;
-
+#ifdef CONFIG_HUGETLB_PAGE
+ int used_hugetlb;
+#endif
/* Architecture-specific MM context */
mm_context_t context;
_
--
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