The patch titled
Subject: userfaultfd: hugetlbfs: reserve count on error in __mcopy_atomic_hugetlb
has been added to the -mm tree. Its filename is
userfaultfd-hugetlbfs-reserve-count-on-error-in-__mcopy_atomic_hugetlb.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-hugetlbfs-reserve-count-on-error-in-__mcopy_atomic_hugetlb.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-hugetlbfs-reserve-count-on-error-in-__mcopy_atomic_hugetlb.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Subject: userfaultfd: hugetlbfs: reserve count on error in __mcopy_atomic_hugetlb
If __mcopy_atomic_hugetlb exits with an error, put_page will be called if
a huge page was allocated and needs to be freed. If a reservation was
associated with the huge page, the PagePrivate flag will be set. Clear
PagePrivate before calling put_page/free_huge_page so that the global
reservation count is not incremented.
Link: http://lkml.kernel.org/r/20161216144821.5183-26-aarcange@xxxxxxxxxx
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Michael Rapoport <RAPOPORT@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/userfaultfd.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff -puN mm/userfaultfd.c~userfaultfd-hugetlbfs-reserve-count-on-error-in-__mcopy_atomic_hugetlb mm/userfaultfd.c
--- a/mm/userfaultfd.c~userfaultfd-hugetlbfs-reserve-count-on-error-in-__mcopy_atomic_hugetlb
+++ a/mm/userfaultfd.c
@@ -301,8 +301,23 @@ retry:
out_unlock:
up_read(&dst_mm->mmap_sem);
out:
- if (page)
+ if (page) {
+ /*
+ * We encountered an error and are about to free a newly
+ * allocated huge page. It is possible that there was a
+ * reservation associated with the page that has been
+ * consumed. See the routine restore_reserve_on_error
+ * for details. Unfortunately, we can not call
+ * restore_reserve_on_error now as it would require holding
+ * mmap_sem. Clear the PagePrivate flag so that the global
+ * reserve count will not be incremented in free_huge_page.
+ * The reservation map will still indicate the reservation
+ * was consumed and possibly prevent later page allocation.
+ * This is better than leaking a global reservation.
+ */
+ ClearPagePrivate(page);
put_page(page);
+ }
BUG_ON(copied < 0);
BUG_ON(err > 0);
BUG_ON(!copied && !err);
_
Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are
userfaultfd-hugetlbfs-add-copy_huge_page_from_user-for-hugetlb-userfaultfd-support.patch
userfaultfd-hugetlbfs-add-hugetlb_mcopy_atomic_pte-for-userfaultfd-support.patch
userfaultfd-hugetlbfs-add-__mcopy_atomic_hugetlb-for-huge-page-uffdio_copy.patch
userfaultfd-hugetlbfs-fix-__mcopy_atomic_hugetlb-retry-error-processing.patch
userfaultfd-hugetlbfs-add-userfaultfd-hugetlb-hook.patch
userfaultfd-hugetlbfs-allow-registration-of-ranges-containing-huge-pages.patch
userfaultfd-hugetlbfs-add-userfaultfd_hugetlb-test.patch
userfaultfd-hugetlbfs-userfaultfd_huge_must_wait-for-hugepmd-ranges.patch
userfaultfd-hugetlbfs-reserve-count-on-error-in-__mcopy_atomic_hugetlb.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
