[PATCH v2 00/13] libmultipath: a generic multipath lib for block drivers

[John Garry]

libmultipath: a generic multipath lib for block drivers

This series introduces libmultipath. It is essentially a refactoring of
NVME multipath support, so we can have a common library to also support
native SCSI multipath.

Much of the code is taken directly from the NVMe multipath code. However,
NVMe specifics are removed. A template structure is provided so the driver
may provide callbacks for driver specifics, like ANA support for NVMe.

Important new structures introduced include:

- mpath_head
These contain much of the multipath-specific functionality from
nvme_ns_head, including a pointer to the gendisk structure and
a path SRCU-based array.

- mpath_device
This is the per-path structure, and contains much the same
multipath-specific functionality in nvme_ns

libmultipath provides functionality for path management, path selection,
data path, and failover handling.

Since the NVMe driver has some code in the sysfs and ioctl handling
which iterate all multipath NSes, functions like mpath_call_for_device()
are added to do the same per-path iteration.

Full series also available at
https://github.com/johnpgarry/linux/commits/scsi-multipath-pre-7.1-upstream-v2/

Differences to v1:
- put current_path[] at end of struct mpath_head (Nilay)
- drop struct mpath_disk and keep nvme_remove_head() (Nilay)
- don't pass iopolicy from mpath_find_path() (Benjamin)
- change mpath_access_state names (Nilay)
- fix for setting mpath_device.nr_active and .numa_node (Nilay)
- fix uninit'ed pointers in __mpath_find_path() (Nilay)
- simplify mpath_head_template.available_path (Nilay, Benjamin)
- use DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE (Benjamin)
- check mpath_bdev_submit_bio() -> .clone_bio() for errors (Benjamin)
- drop struct mpath_pr_ops (Keith)
- drop mpath_head_template.bdev_ioctl
- drop mpath_head_template.get_unique_id
- drop mpath_head_template.report_zones
- drop mpath_head_template.get_access_state
- add mpath_head_template.ioctl_{begin, finish} and drop
mpath_head_read_unlock()
- add mpath_device.access_state
- add mpath_head_devices_empty()
- make mpath_delete_device() return a bool

John Garry (13):
  libmultipath: Add initial framework
  libmultipath: Add basic gendisk support
  libmultipath: Add path selection support
  libmultipath: Add bio handling
  libmultipath: Add support for mpath_device management
  libmultipath: Add cdev support
  libmultipath: Add delayed removal support
  libmultipath: Add sysfs helpers
  libmultipath: Add PR support
  libmultipath: Add mpath_bdev_report_zones()
  libmultipath: Add support for block device IOCTL
  libmultipath: Add mpath_bdev_getgeo()
  libmultipath: Add mpath_bdev_get_unique_id()

 include/linux/multipath.h |  181 ++++++
 lib/Kconfig               |    6 +
 lib/Makefile              |    2 +
 lib/multipath.c           | 1293 +++++++++++++++++++++++++++++++++++++
 4 files changed, 1482 insertions(+)
 create mode 100644 include/linux/multipath.h
 create mode 100644 lib/multipath.c

-- 
2.43.5