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c17ba40c37
offline_and_remove_memory() handles a single contiguous range.
Callers that manage a device composed of several ranges (dax/kmem)
currently have to call it in a loop, which gives up atomicity.
In addition to pushing rollback logic into the driver, the lack of
atomicity creates a race condition between system daemons trying to manage
the same resource:
- Manager 1: Offlines memory blocks. Removes device.
^^^^
- Manager 2: Detects offline memory blocks, re-onlines them.
Add offline_and_remove_memory_ranges(), which takes an array of ranges and
processes them as one operation under a single lock_device_hotplug():
- Phase 1 offlines every block of every range.
- Phase 2 removes the ranges only if all ranges are offline.
- If any offline fails, the whole operation is reverted.
This gives callers all-or-nothing semantics for the offline step, so a
failed or interrupted unplug leaves the device in a consistent state.
This also resolves the battling managers race - the second manager's
operation simply fails when the block is destroyed / cannot be onlined.
offline_and_remove_memory() becomes a thin wrapper that passes its single
range to the new helper, so the offline/rollback logic lives in one place.
Link: https://lore.kernel.org/20260712154505.3564379-7-gourry@gourry.net
Signed-off-by: Gregory Price <gourry@gourry.net>
Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Dan Williams <djbw@kernel.org>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pankaj Gupta <pankaj.gupta@amd.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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