[RFC PATCH 0/8] dax: Add a dax-rmap tree to support reflink

[Shiyang Ruan]

This patchset is a try to resolve the shared 'page cache' problem for
fsdax.

In order to track multiple mappings and indexes on one page, I
introduced a dax-rmap rb-tree to manage the relationship.  A dax entry
will be associated more than once if is shared.  At the second time we
associate this entry, we create this rb-tree and store its root in
page->private(not used in fsdax).  Insert (->mapping, ->index) when
dax_associate_entry() and delete it when dax_disassociate_entry().

We can iterate the dax-rmap rb-tree before any other operations on
mappings of files.  Such as memory-failure and rmap.

Same as before, I borrowed and made some changes on Goldwyn's patchsets.
These patches makes up for the lack of CoW mechanism in fsdax.

The rests are dax & reflink support for xfs.

(Rebased to 5.7-rc2)


Shiyang Ruan (8):
  fs/dax: Introduce dax-rmap btree for reflink
  mm: add dax-rmap for memory-failure and rmap
  fs/dax: Introduce dax_copy_edges() for COW
  fs/dax: copy data before write
  fs/dax: replace mmap entry in case of CoW
  fs/dax: dedup file range to use a compare function
  fs/xfs: handle CoW for fsdax write() path
  fs/xfs: support dedupe for fsdax

 fs/dax.c               | 343 +++++++++++++++++++++++++++++++++++++----
 fs/ocfs2/file.c        |   2 +-
 fs/read_write.c        |  11 +-
 fs/xfs/xfs_bmap_util.c |   6 +-
 fs/xfs/xfs_file.c      |  10 +-
 fs/xfs/xfs_iomap.c     |   3 +-
 fs/xfs/xfs_iops.c      |  11 +-
 fs/xfs/xfs_reflink.c   |  79 ++++++----
 include/linux/dax.h    |  11 ++
 include/linux/fs.h     |   9 +-
 mm/memory-failure.c    |  63 ++++++--
 mm/rmap.c              |  54 +++++--
 12 files changed, 498 insertions(+), 104 deletions(-)

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2.26.2