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Commit 409eb8c2 authored by Hillf Danton's avatar Hillf Danton Committed by Linus Torvalds
Browse files

mm/hugetlb.c: undo change to page mapcount in fault handler 



Page mapcount should be updated only if we are sure that the page ends
up in the page table otherwise we would leak if we couldn't COW due to
reservations or if idx is out of bounds.

Signed-off-by: default avatarHillf Danton <dhillf@gmail.com>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6568d4a9

mm/hugetlb.c

+6 −3
Original line number Diff line number Diff line
@@ -2508,6 +2508,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma, 
{

	struct hstate *h = hstate_vma(vma);

	int ret = VM_FAULT_SIGBUS;

	int anon_rmap = 0;

	pgoff_t idx;

	unsigned long size;

	struct page *page;
@@ -2562,14 +2563,13 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma, 
			spin_lock(&inode->i_lock);

			inode->i_blocks += blocks_per_huge_page(h);

			spin_unlock(&inode->i_lock);

			page_dup_rmap(page);

		} else {

			lock_page(page);

			if (unlikely(anon_vma_prepare(vma))) {

				ret = VM_FAULT_OOM;

				goto backout_unlocked;

			}

			hugepage_add_new_anon_rmap(page, vma, address);

			anon_rmap = 1;

		}

	} else {

		/*
@@ -2582,7 +2582,6 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma, 
			      VM_FAULT_SET_HINDEX(h - hstates);

			goto backout_unlocked;

		}

		page_dup_rmap(page);

	}



	/*
@@ -2606,6 +2605,10 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma, 
	if (!huge_pte_none(huge_ptep_get(ptep)))

		goto backout;



	if (anon_rmap)

		hugepage_add_new_anon_rmap(page, vma, address);

	else

		page_dup_rmap(page);

	new_pte = make_huge_pte(vma, page, ((vma->vm_flags & VM_WRITE)

				&& (vma->vm_flags & VM_SHARED)));

	set_huge_pte_at(mm, address, ptep, new_pte);