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Aneesh Kumar K.V 024eee0e83 mm: page_mkclean vs MADV_DONTNEED race
MADV_DONTNEED is handled with mmap_sem taken in read mode.  We call
page_mkclean without holding mmap_sem.

MADV_DONTNEED implies that pages in the region are unmapped and subsequent
access to the pages in that range is handled as a new page fault.  This
implies that if we don't have parallel access to the region when
MADV_DONTNEED is run we expect those range to be unallocated.

w.r.t page_mkclean() we need to make sure that we don't break the
MADV_DONTNEED semantics.  MADV_DONTNEED check for pmd_none without holding
pmd_lock.  This implies we skip the pmd if we temporarily mark pmd none.
Avoid doing that while marking the page clean.

Keep the sequence same for dax too even though we don't support
MADV_DONTNEED for dax mapping

The bug was noticed by code review and I didn't observe any failures w.r.t
test run.  This is similar to

commit 58ceeb6bec
Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Date:   Thu Apr 13 14:56:26 2017 -0700

    thp: fix MADV_DONTNEED vs. MADV_FREE race

commit ced108037c
Author: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Date:   Thu Apr 13 14:56:20 2017 -0700

    thp: fix MADV_DONTNEED vs. numa balancing race

Link: http://lkml.kernel.org/r/20190321040610.14226-1-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc:"Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-05-14 09:47:48 -07:00
arch hugetlb: allow to free gigantic pages regardless of the configuration 2019-05-14 09:47:47 -07:00
block
certs
crypto
Documentation mm: move recent_rotated pages calculation to shrink_inactive_list() 2019-05-14 09:47:45 -07:00
drivers IB/mthca: use the new FOLL_LONGTERM flag to get_user_pages_fast() 2019-05-14 09:47:46 -07:00
fs mm: page_mkclean vs MADV_DONTNEED race 2019-05-14 09:47:48 -07:00
include mm: introduce put_user_page*(), placeholder versions 2019-05-14 09:47:47 -07:00
init init: free_initmem: poison freed init memory 2019-05-14 09:47:47 -07:00
ipc
kernel mm/gup: change GUP fast to use flags rather than a write 'bool' 2019-05-14 09:47:46 -07:00
lib mm/gup: change GUP fast to use flags rather than a write 'bool' 2019-05-14 09:47:46 -07:00
LICENSES
mm mm: page_mkclean vs MADV_DONTNEED race 2019-05-14 09:47:48 -07:00
net mm/gup: change GUP fast to use flags rather than a write 'bool' 2019-05-14 09:47:46 -07:00
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.cocciconfig
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Linux kernel
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Please read the Documentation/process/changes.rst file, as it contains the
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