[PATCH 0/3] Fix read-only THP for non-tmpfs filesystems

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

As described more verbosely in the [3/3] changelog, we can
inadvertently put an order-0 page in the page cache which
occupies 512 consecutive entries.  Users are running into
this if they enable the READ_ONLY_THP_FOR_FS config option;
see https://bugzilla.kernel.org/show_bug.cgi?id=206569
and Qian Cai has also reported it here:
https://lore.kernel.org/lkml/20200616013309.GB815@lca.pw/

This is a rather intrusive way of fixing the problem, but has the
advantage that I've actually been testing it with the THP patches,
which means that it sees far more use than it does upstream -- indeed,
Song has been entirely unable to reproduce it.  It also has the advantage
that it removes a few patches from my gargantuan backlog of THP patches.

Matthew Wilcox (Oracle) (3):
  XArray: Add xa_get_order
  XArray: Add xas_split
  mm/filemap: Fix storing to a THP shadow entry

 Documentation/core-api/xarray.rst |  16 +--
 include/linux/xarray.h            |  22 ++++
 lib/test_xarray.c                 |  62 ++++++++++
 lib/xarray.c                      | 196 ++++++++++++++++++++++++++++--
 mm/filemap.c                      |  42 +++++--
 5 files changed, 311 insertions(+), 27 deletions(-)

-- 
2.28.0