[ndctl,v7,00/13] daxctl: add a new reconfigure-device command

Message

Verma, Vishal L July 24, 2019, 9:57 p.m. UTC

Changes in v7:
- Fix a couple of checkaptch type errors in the new lines added in v6 (Dan).
- Get rid of daxctl_dev_get_mode. daxctl_dev_get_memory is sufficient to
  both check the mode and allocate the memory related structures on its
  first call. (Dan)
- Due to the above, daxctl_dev_mode is now private to libdaxctl, and not
  part of the API exported through libdaxctl.h
- Add a large enough buffer at init time to construct dynamic paths, and avoid
  asprintf() type allocations for memory blocks at runtime (Dan).

Changes in v6:
- For memory block online/offline operations, the kernel responds with
  an EINVAL for both 'real' errors, and if the memory was already in the
  requested state. Since there is a TOCTOU hole between checking the
  state and storing it, just perform a second check if the store results
  in an error. If the check shows the state to be the same as the one
  we're attempting, it means that another agent (usually udev) won the
  race, but we don't care so long as the state change happened, so don't
  report an error. (Fan Du)

Changes in v5:
 - device.c: correctly set loglevel for daxctl_ctx for --verbose
 - drop the subsys caching, its complexity started to exceed its
   benefit. dax-class device models will simply error out during
   reconfigure. (Dan)
 - Add a note to the man page for the above.
 - Clarify the onlining policy (online_movable) in the man page
 - rename "numa_node" to "target_node" in device listings (Dan)
 - When printing a device 'mode', assume devdax if !system-ram,
   avoiding a "mode: unknown" situation which can be confusing. (Dan)
 - Add a "state: disabled" attribute to the device listing if a driver
   is not bound. This is more apt than the previous "mode: unknown"
   listing.
 - add an api to get 'dev->resource' parsing /proc/iomem as a
   fallback for when the kernel doesn't provide the attribute (Dan)
 - convert node_* apis to 'memory_* apis that act on a new daxctl_memory
   object (Dan)
 - online only memory sections belonging to the device in question by
   cross referencing block indices with the dax device resource (Dan)
 - Refuse to reconfigure a device that is already in the target mode.
   Until now, reconfiguring a system-ram device back to system-ram would
   result in a 'online memory may not be hot-removed' kernel warning.
 - If the device was already in the system-ram mode, skip
   disabling/enabling, but still try to online the memory unless the
   --no-online option is in effect.
 - In daxctl_unbind, also 'remove_id' to prevent devices automatically
   binding to the kmem driver on a disable + re-enable, which can be
   surprising (Dan).
 - Rewrite the top half of daxctl/device.c to borrow elements from
   ndctl/namespace.c so that it can support growing additional commands
   that operate on devices (online-memory and offline-memory)
 - Refactor the bottom half of daxctl/device.c so we only do the
   disabling/offlining steps if the device was enabled.
 - Add new commands to online and offline memory sections (Dan)
   associated with a given dax device (Dan)
 - Add a new test - daxctl-device.sh - to test daxctl reconfigure-device,
   online-memory, and offline-memory commands.
 - Add an example in documentation demonstrating how to use numactl
   to bind a process to a node surfaced from a dax device (Andy Rudoff)

Changes in v4:
 - Don't fail add_dax_dev for kmod failures. Instead fail only when the kmod
   list is actually used, i.e. during daxctl-reconfigure-device

Changes in v3:
 - In daxctl_dev_get_mode(), remove the subsystem warning, detect dax-class
   and simply make it return devdax

Changes in v2:
 - Add examples to the documentation page (Dave Hansen)
 - Clarify documentation regarding the conversion from system-ram to devdax
 - Remove any references to a persistent config from the documentation -
   those can be added when the feature is added.
 - device.c: validate option compatibility
 - daxctl-list: display numa_node for device listings
 - daxctl-list: display mode for device listings
 - make the options more consistent by adding a '-O' short option
   for --attempt-offline

Add a new daxctl-reconfigure-device command that lets us reconfigure DAX
devices back and forth between 'system-ram' and 'device-dax' modes. It
also includes facilities to online any newly hot-plugged memory
(default), and attempt to offline memory before converting away from the
system-ram mode (not default, requires a --attempt-offline option).

Currently missing from this series is a way to persistently store which
devices have been 'marked' for use as system-ram. This depends on a
config system overhaul in ndctl, and patches for those will follow
separately and are independent of this work.

Example invocations:

1. Reconfigure dax0.0 to system-ram mode, don’t online the memory
    # daxctl reconfigure-device --mode=system-ram --no-online dax0.0
    [
      {
        "chardev":"dax0.0",
        "size":16777216000,
        "target_node":2,
        "mode":"system-ram"
      }
    ]

2. Reconfigure dax0.0 to devdax mode, attempt to offline the memory
    # daxctl reconfigure-device --human --mode=devdax --attempt-offline dax0.0
    {
      "chardev":"dax0.0",
      "size":"15.63 GiB (16.78 GB)",
      "target_node":2,
      "mode":"devdax"
    }

3. Reconfigure all dax devices on region0 to system-ram mode
    # daxctl reconfigure-device --mode=system-ram --region=0 all
    [
      {
        "chardev":"dax0.0",
        "size":16777216000,
        "target_node":2,
        "mode":"system-ram"
      },
      {
        "chardev":"dax0.1",
        "size":16777216000,
        "target_node":3,
        "mode":"system-ram"
      }
    ]

These patches can also be found in the 'kmem-pending' branch on github:
https://github.com/pmem/ndctl/tree/kmem-pending

Cc: Dan Williams <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Pavel Tatashin <[e-mail]>

Vishal Verma (13):
  libdaxctl: add interfaces to get ctx and check device state
  libdaxctl: add interfaces to enable/disable devices
  libdaxctl: add an interface to retrieve the device resource
  libdaxctl: add a 'daxctl_memory' object for memory based operations
  daxctl/list: add target_node for device listings
  daxctl/list: display the mode for a dax device
  daxctl: add a new reconfigure-device command
  Documentation/daxctl: add a man page for daxctl-reconfigure-device
  daxctl: add commands to online and offline memory
  Documentation: Add man pages for daxctl-{on,off}line-memory
  contrib/ndctl: fix region-id completions for daxctl
  contrib/ndctl: add bash-completion for the new daxctl commands
  test: Add a unit test for daxctl-reconfigure-device and friends

 Documentation/daxctl/Makefile.am              |   5 +-
 .../daxctl/daxctl-offline-memory.txt          |  72 ++
 Documentation/daxctl/daxctl-online-memory.txt |  80 ++
 .../daxctl/daxctl-reconfigure-device.txt      | 139 ++++
 Makefile.am                                   |   3 +-
 contrib/ndctl                                 |  38 +-
 daxctl/Makefile.am                            |   2 +
 daxctl/builtin.h                              |   3 +
 daxctl/daxctl.c                               |   3 +
 daxctl/device.c                               | 476 ++++++++++++
 daxctl/lib/Makefile.am                        |   5 +-
 daxctl/lib/libdaxctl-private.h                |  38 +
 daxctl/lib/libdaxctl.c                        | 685 ++++++++++++++++++
 daxctl/lib/libdaxctl.sym                      |  18 +
 daxctl/libdaxctl.h                            |  16 +
 test/Makefile.am                              |   3 +-
 test/common                                   |  19 +-
 test/daxctl-devices.sh                        |  81 +++
 util/iomem.c                                  |  37 +
 util/iomem.h                                  |  12 +
 util/json.c                                   |  22 +
 21 files changed, 1743 insertions(+), 14 deletions(-)
 create mode 100644 Documentation/daxctl/daxctl-offline-memory.txt
 create mode 100644 Documentation/daxctl/daxctl-online-memory.txt
 create mode 100644 Documentation/daxctl/daxctl-reconfigure-device.txt
 create mode 100644 daxctl/device.c
 create mode 100755 test/daxctl-devices.sh
 create mode 100644 util/iomem.c
 create mode 100644 util/iomem.h