On Tue, 15 Jul 2014 15:58:32 +0400 Konstantin Khlebnikov <[email protected]> wrote:
> From: Konstantin Khlebnikov <[email protected]> > > Faulting around non-linear page-fault has no sense and > breaks logic in do_fault_around because pgoff is shifted. > Please be a lot more careful with the changelogs? This one failed to describe the effects of the bug, failed to adequately describe the bug itself, failed to describe the offending commits and failed to identify which kernel versions need the patch. Sigh. I went back and assembled the necessary information, below. Please check it. From: Konstantin Khlebnikov <[email protected]> Subject: 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 d7c1755179b82d ("mm: implement ->map_pages for shmem/tmpfs"), although the bug was actually added by 8c6e50b0290c4 ("mm: introduce vm_ops->map_pages()"). Problem is caused by calling do_fault_around for _non-linear_ faiult. In this case pgoff is shifted and might become negative during calculation. Faulting around non-linear page-fault has no sense and breaks logic in do_fault_around because pgoff is shifted. Signed-off-by: Konstantin Khlebnikov <[email protected]> Reported-by: "Ingo Korb" <[email protected]> Tested-by: "Ingo Korb" <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Sasha Levin <[email protected]> Cc: Dave Jones <[email protected]> Cc: Ning Qu <[email protected]> Cc: "Kirill A. Shutemov" <[email protected]> Cc: <[email protected]> [3.15.x] Signed-off-by: Andrew Morton <[email protected]> --- mm/memory.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff -puN mm/memory.c~mm-do-not-call-do_fault_around-for-non-linear-fault mm/memory.c --- a/mm/memory.c~mm-do-not-call-do_fault_around-for-non-linear-fault +++ a/mm/memory.c @@ -2882,7 +2882,8 @@ static int do_read_fault(struct mm_struc * 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)) _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
