mm: hugetlb: initialize PG_reserved for tail pages of gigantic compound pages
Commit 11feeb49 ("kvm: optimize away THP checks in kvm_is_mmio_pfn()") introduced a memory leak when KVM is run on gigantic compound pages. That commit depends on the assumption that PG_reserved is identical for all head and tail pages of a compound page. So that if get_user_pages returns a tail page, we don't need to check the head page in order to know if we deal with a reserved page that requires different refcounting. The assumption that PG_reserved is the same for head and tail pages is certainly correct for THP and regular hugepages, but gigantic hugepages allocated through bootmem don't clear the PG_reserved on the tail pages (the clearing of PG_reserved is done later only if the gigantic hugepage is freed). This patch corrects the gigantic compound page initialization so that we can retain the optimization in 11feeb49 . The cacheline was already modified in order to set PG_tail so this won't affect the boot time of large memory systems. [akpm@linux-foundation.org: tweak comment layout and grammar] Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Reported-by: andy123 <ajs124.ajs124@gmail.com> Acked-by: Rik van Riel <riel@redhat.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Acked-by: Rafael Aquini <aquini@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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