Commit c118678b authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Linus Torvalds

mm: do not call do_fault_around for non-linear fault

Ingo Korb reported that "repeated mapping of the same file on tmpfs
using remap_file_pages sometimes triggers a BUG at mm/filemap.c:202 when
the process exits".

He bisected the bug to d7c17551 ("mm: implement ->map_pages for
shmem/tmpfs"), although the bug was actually added by commit
8c6e50b0 ("mm: introduce vm_ops->map_pages()").

The problem is caused by calling do_fault_around for a _non-linear_
fault.  In this case pgoff is shifted and might become negative during

Faulting around non-linear page-fault makes no sense and breaks the
logic in do_fault_around because pgoff is shifted.
Signed-off-by: default avatarKonstantin Khlebnikov <>
Reported-by: default avatarIngo Korb <>
Tested-by: default avatarIngo Korb <>
Cc: Hugh Dickins <>
Cc: Sasha Levin <>
Cc: Dave Jones <>
Cc: Ning Qu <>
Cc: "Kirill A. Shutemov" <>
Cc: <>	[3.15.x]
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent b1923b55
......@@ -2882,7 +2882,8 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
* if page by the offset is not ready to be mapped (cold cache or
* something).
if (vma->vm_ops->map_pages && fault_around_pages() > 1) {
if (vma->vm_ops->map_pages && !(flags & FAULT_FLAG_NONLINEAR) &&
fault_around_pages() > 1) {
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
do_fault_around(vma, address, pte, pgoff, flags);
if (!pte_same(*pte, orig_pte))
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment