This patchset is a try to resolve the problem of tracking shared page
for fsdax.
Instead of per-page tracking method, this patchset introduces a query
interface: get_shared_files(), which is implemented by each FS, to
obtain the owners of a shared page. It returns an owner list of this
shared page. Then, the memory-failure() iterates the list to be able
to notify each process using files that sharing this page.
The design of the tracking method is as follow:
1. dax_assocaite_entry() associates the owner's info to this page
- For non-reflink case:
page->mapping,->index stores the file's mapping, offset in file.
A dax page is not shared by other files. dax_associate_entry() is
called only once. So, use page->mapping,->index to store the
owner's info.
- For reflink case:
page->mapping,->index stores the block device, offset in device.
A dax page is shared more than once. So, dax_assocaite_entry()
will be called more than once. We introduce page->zone_device_data
as reflink counter, to indicate that this page is shared and how
many owners now is using this page. The page->mapping,->index is
used to store the block_device of the fs and page offset of this
device.
2. dax_lock_page() calls query interface to lock each dax entry
- For non-reflink case:
owner's info is stored in page->mapping,->index.
So, It is easy to lock its dax entry.
- For reflink case:
owner's info is obtained by calling get_shared_files(), which is
implemented by FS.
The FS context could be found in block_device that stored by
page->mapping. Then lock the dax entries of the owners.
In memory-failure(), since the owner list has been obtained in
dax_lock_page(), just iterate the list and handle the error. This
patchset didn't handle the memory failure on metadata of FS because
I haven't found a way to distinguish whether this page contains
matadata yet. Still working on it.
==
I also 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 on v5.8)
==
Shiyang Ruan (8):
fs: introduce get_shared_files() for dax&reflink
fsdax, mm: track files sharing dax page for memory-failure
fsdax: introduce dax_copy_edges() for COW
fsdax: copy data before write
fsdax: replace mmap entry in case of CoW
fsdax: dedup file range to use a compare function
fs/xfs: handle CoW for fsdax write() path
fs/xfs: support dedupe for fsdax
fs/btrfs/reflink.c | 3 +-
fs/dax.c | 302 +++++++++++++++++++++++++++++++++++------
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 | 80 ++++++-----
fs/xfs/xfs_super.c | 67 +++++++++
include/linux/dax.h | 18 ++-
include/linux/fs.h | 11 +-
include/linux/mm.h | 8 ++
mm/memory-failure.c | 138 ++++++++++++-------
14 files changed, 529 insertions(+), 141 deletions(-)
--
2.27.0
