mm: simplify find_vma_prev() (6bd4837d) · Commits · 戴 / test

commit ("mm: make the vma list be doubly linked") added the vm_prev member to vm_area_struct. We can simplify find_vma_prev() by using it. Also, this change helps to improve page fault performance because it has stronger locality of reference. Signed-off-by:

KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by:

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Hugh Dickins <hughd@google.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Shaohua Li <shaohua.li@intel.com> Cc: Michal Hocko <mhocko@suse.cz> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/mmap.c

+8 −28

Original line number	Diff line number	Diff line
		@@ -1603,39 +1603,19 @@ struct vm_area_struct find_vma(struct mm_struct mm, unsigned long addr)

		EXPORT_SYMBOL(find_vma);

		/* Same as find_vma, but also return a pointer to the previous VMA in pprev. /
		/*
		* Same as find_vma, but also return a pointer to the previous VMA in *pprev.
		* Note: pprev is set to NULL when return value is NULL.
		*/
		struct vm_area_struct *
		find_vma_prev(struct mm_struct *mm, unsigned long addr,
		struct vm_area_struct **pprev)
		{
		struct vm_area_struct vma = NULL, prev = NULL;
		struct rb_node *rb_node;
		if (!mm)
		goto out;

		/* Guard against addr being lower than the first VMA */
		vma = mm->mmap;

		/* Go through the RB tree quickly. */
		rb_node = mm->mm_rb.rb_node;

		while (rb_node) {
		struct vm_area_struct *vma_tmp;
		vma_tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);

		if (addr < vma_tmp->vm_end) {
		rb_node = rb_node->rb_left;
		} else {
		prev = vma_tmp;
		if (!prev->vm_next \|\| (addr < prev->vm_next->vm_end))
		break;
		rb_node = rb_node->rb_right;
		}
		}
		struct vm_area_struct *vma;

		out:
		*pprev = prev;
		return prev ? prev->vm_next : vma;
		vma = find_vma(mm, addr);
		*pprev = vma ? vma->vm_prev : NULL;
		return vma;
		}

		/*

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