mm/thp: ClearPageDoubleMap in first page_add_file_rmap()
authorHugh Dickins <hughd@google.com>
Tue, 22 Mar 2022 21:47:40 +0000 (14:47 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 22 Mar 2022 22:57:11 +0000 (15:57 -0700)
commitbd55b0c2d64e84a75575f548a33a3dfecc135b65
tree5058ecd90eded623d985eca96a08d9ce664b8ffb
parent734c15700cdf9062ae98d8b131c6fe873dfad26d
mm/thp: ClearPageDoubleMap in first page_add_file_rmap()

PageDoubleMap is maintained differently for anon and for shmem+file: the
shmem+file one was never cleared, because a safe place to do so could
not be found; so it would blight future use of the cached hugepage until
evicted.

See https://lore.kernel.org/lkml/1571938066-29031-1-git-send-email-yang.shi@linux.alibaba.com/

But page_add_file_rmap() does provide a safe place to do so (though later
than one might wish): allowing testing to return to an initial state
without a damaging drop_caches.

Link: https://lkml.kernel.org/r/61c5cf99-a962-9a25-597a-53ab1bd8fbc0@google.com
Fixes: 9a73f61bdb8a ("thp, mlock: do not mlock PTE-mapped file huge pages")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/rmap.c