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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@redhat.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Mike Kravetz 2017-02-22 15:43:16 -08:00 committed by Linus Torvalds
parent 87ffc118b5
commit 21205bf8f7
1 changed files with 16 additions and 1 deletions
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17
mm/userfaultfd.c
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@ -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);