[PATCH] kill mm_struct.used_hugetlb

mm_struct.used_hugetlb used to eliminate costly find_vma() from
follow_page().  Now it is used only in ia64 version of follow_huge_addr(). 
I know nothing about ia64, but this REGION_NUMBER() looks simple enough to
kill used_hugetlb.

There is debug version (commented out) of follow_huge_addr() in i386 which
looks at used_hugetlb, but it can work without this check.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/mm/hugetlbpage.c

@@ -146,9 +146,6 @@ follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
 	struct page *page;
 	struct vm_area_struct *vma;
 
-	if (! mm->used_hugetlb)
-		return ERR_PTR(-EINVAL);
-
 	vma = find_vma(mm, addr);
 	if (!vma || !is_vm_hugetlb_page(vma))
 		return ERR_PTR(-EINVAL);

arch/ia64/mm/hugetlbpage.c

@@ -158,8 +158,6 @@ struct page *follow_huge_addr(struct mm_struct *mm, unsigned long addr, int writ
 	struct page *page;
 	pte_t *ptep;
 
-	if (! mm->used_hugetlb)
-		return ERR_PTR(-EINVAL);
 	if (REGION_NUMBER(addr) != REGION_HPAGE)
 		return ERR_PTR(-EINVAL);
 

include/linux/hugetlb.h

@@ -35,13 +35,6 @@ extern unsigned long max_huge_pages;
 extern const unsigned long hugetlb_zero, hugetlb_infinity;
 extern int sysctl_hugetlb_shm_group;
 
-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;
-}
-
 #ifndef ARCH_HAS_HUGEPAGE_ONLY_RANGE
 #define is_hugepage_only_range(addr, len)	0
 #define hugetlb_free_pgtables(tlb, prev, start, end) do { } while (0)
@@ -74,7 +67,6 @@ static inline unsigned long hugetlb_total_pages(void)
 #define is_hugepage_mem_enough(size)		0
 #define hugetlb_report_meminfo(buf)		0
 #define hugetlb_report_node_meminfo(n, buf)	0
-#define mark_mm_hugetlb(mm, vma)		do { } while (0)
 #define follow_huge_pmd(mm, addr, pmd, write)	NULL
 #define is_aligned_hugepage_range(addr, len)	0
 #define prepare_hugepage_range(addr, len)	(-EINVAL)

include/linux/sched.h

@@ -215,9 +215,6 @@ struct mm_struct {
 	unsigned long saved_auxv[40]; /* for /proc/PID/auxv */
 
 	unsigned dumpable:1;
-#ifdef CONFIG_HUGETLB_PAGE
-	int used_hugetlb;
-#endif
 	cpumask_t cpu_vm_mask;
 
 	/* Architecture-specific MM context */

mm/mmap.c

@@ -317,7 +317,6 @@ static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
 	if (mapping)
 		spin_unlock(&mapping->i_mmap_lock);
 
-	mark_mm_hugetlb(mm, vma);
 	mm->map_count++;
 	validate_mm(mm);
 }