[RFC,0/4] fsdax: introduce fs query to support reflink

Message

Ruan Shiyang Sept. 15, 2020, 10:13 a.m. UTC

This patchset is a try to resolve the problem of tracking shared page
for fsdax.

This patchset moves owner tracking from dax_assocaite_entry() to pmem
device, by introducing an interface ->memory_failure() of struct
pagemap.  The interface is called by memory_failure() in mm, and
implemented by pmem device.  Then pmem device find the filesystem
which the damaged page located in, and call ->storage_lost() to track
files or metadata assocaited with this page.  Finally we are able to
try to fix the damaged data in filesystem and do other necessary
processing, such as killing processes who are using the files
affected.

The call trace is like this:
 memory_failure()
   pgmap->ops->memory_failure()      => pmem_pgmap_memory_failure()
     bdev->bd_super->storage_lost()  => xfs_fs_storage_lost()
       xfs_rmap_query_range()
         xfs_storage_lost_helper()
           mf_recover_controller->recover_fn => \ 
                            memory_failure_dev_pagemap_kill_procs()

The collect_procs() and kill_procs() are moved into a callback which
is passed from memory_failure() to xfs_storage_lost_helper().  So we
can call it when a file assocaited is found, instead of creating a
file list and iterate it.

The fsdax & reflink support for XFS is not contained in this patchset.

(Rebased on v5.9-rc2)
==

Shiyang Ruan (4):
  fs: introduce ->storage_lost() for memory-failure
  pagemap: introduce ->memory_failure()
  mm, fsdax: refactor dax handler in memory-failure
  fsdax: remove useless (dis)associate functions

 block/genhd.c            |  12 ++++
 drivers/nvdimm/pmem.c    |  31 ++++++++++
 fs/dax.c                 |  64 ++------------------
 fs/xfs/xfs_super.c       |  80 ++++++++++++++++++++++++
 include/linux/dax.h      |   5 +-
 include/linux/fs.h       |   1 +
 include/linux/genhd.h    |   2 +
 include/linux/memremap.h |   3 +
 include/linux/mm.h       |  14 +++++
 mm/memory-failure.c      | 127 ++++++++++++++++++++++++---------------
 10 files changed, 229 insertions(+), 110 deletions(-)