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Commit 6c6d5280 authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by Linus Torvalds
Browse files

pagewalk: don't look up vma if walk->hugetlb_entry is unused 



Currently, walk_page_range() calls find_vma() every page table for walk
iteration.  but it's completely unnecessary if walk->hugetlb_entry is
unused.  And we don't have to assume find_vma() is a lightweight
operation.  So this patch checks the walk->hugetlb_entry and avoids the
find_vma() call if possible.

This patch also makes some cleanups.  1) remove ugly uninitialized_var()
and 2) #ifdef in function body.

Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4b6ddbf7

mm/pagewalk.c

+37 −6
Original line number Diff line number Diff line
@@ -126,7 +126,39 @@ static int walk_hugetlb_range(struct vm_area_struct *vma, 


	return 0;

}

#endif



static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)

{

	struct vm_area_struct *vma;



	/* We don't need vma lookup at all. */

	if (!walk->hugetlb_entry)

		return NULL;



	VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));

	vma = find_vma(walk->mm, addr);

	if (vma && vma->vm_start <= addr && is_vm_hugetlb_page(vma))

		return vma;



	return NULL;

}



#else /* CONFIG_HUGETLB_PAGE */

static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)

{

	return NULL;

}



static int walk_hugetlb_range(struct vm_area_struct *vma,

			      unsigned long addr, unsigned long end,

			      struct mm_walk *walk)

{

	return 0;

}



#endif /* CONFIG_HUGETLB_PAGE */







/**

 * walk_page_range - walk a memory map's page tables with a callback
@@ -165,18 +197,17 @@ int walk_page_range(unsigned long addr, unsigned long end, 


	pgd = pgd_offset(walk->mm, addr);

	do {

		struct vm_area_struct *uninitialized_var(vma);

		struct vm_area_struct *vma;



		next = pgd_addr_end(addr, end);



#ifdef CONFIG_HUGETLB_PAGE

		/*

		 * handle hugetlb vma individually because pagetable walk for

		 * the hugetlb page is dependent on the architecture and

		 * we can't handled it in the same manner as non-huge pages.

		 */

		vma = find_vma(walk->mm, addr);

		if (vma && vma->vm_start <= addr && is_vm_hugetlb_page(vma)) {

		vma = hugetlb_vma(addr, walk);

		if (vma) {

			if (vma->vm_end < next)

				next = vma->vm_end;

			/*
@@ -189,7 +220,7 @@ int walk_page_range(unsigned long addr, unsigned long end, 
			pgd = pgd_offset(walk->mm, next);

			continue;

		}

#endif



		if (pgd_none_or_clear_bad(pgd)) {

			if (walk->pte_hole)

				err = walk->pte_hole(addr, next, walk);