[PATCH v5 0/7] fsdax,xfs: Add reflink&dedupe support for fsdax

From: Shiyang Ruan
Date: Mon May 10 2021 - 23:09:47 EST

This patchset is attempt to add CoW support for fsdax, and take XFS,
which has both reflink and fsdax feature, as an example.

Changes from V4:
- Fix the mistake of breaking dax layout for two inodes
- Add CONFIG_FS_DAX judgement for fsdax code in remap_range.c
- Fix other small problems and mistakes

Changes from V3:
- Take out the first 3 patches as a cleanup patchset[1], which has been
sent yesterday.
- Fix usage of code in dax_iomap_cow_copy()
- Add comments for macro definitions
- Fix other code style problems and mistakes

One of the key mechanism need to be implemented in fsdax is CoW. Copy
the data from srcmap before we actually write data to the destance
iomap. And we just copy range in which data won't be changed.

Another mechanism is range comparison. In page cache case, readpage()
is used to load data on disk to page cache in order to be able to
compare data. In fsdax case, readpage() does not work. So, we need
another compare data with direct access support.

With the two mechanisms implemented in fsdax, we are able to make reflink
and fsdax work together in XFS.

Some of the patches are picked up from Goldwyn's patchset. I made some
changes to adapt to this patchset.

(Rebased on v5.13-rc1 and patchset[1])
[1]: https://lkml.org/lkml/2021/4/22/575

Shiyang Ruan (7):
fsdax: Introduce dax_iomap_cow_copy()
fsdax: Replace mmap entry in case of CoW
fsdax: Add dax_iomap_cow_copy() for dax_iomap_zero
iomap: Introduce iomap_apply2() for operations on two files
fsdax: Dedup file range to use a compare function
fs/xfs: Handle CoW for fsdax write() path
fs/xfs: Add dax dedupe support

fs/dax.c | 206 +++++++++++++++++++++++++++++++++++------
fs/iomap/apply.c | 52 +++++++++++
fs/iomap/buffered-io.c | 2 +-
fs/remap_range.c | 57 ++++++++++--
fs/xfs/xfs_bmap_util.c | 3 +-
fs/xfs/xfs_file.c | 11 +--
fs/xfs/xfs_inode.c | 66 ++++++++++++-
fs/xfs/xfs_inode.h | 1 +
fs/xfs/xfs_iomap.c | 61 +++++++++++-
fs/xfs/xfs_iomap.h | 4 +
fs/xfs/xfs_iops.c | 7 +-
fs/xfs/xfs_reflink.c | 15 +--
include/linux/dax.h | 7 +-
include/linux/fs.h | 12 ++-
include/linux/iomap.h | 7 +-
15 files changed, 449 insertions(+), 62 deletions(-)