Let's offline+remove memory blocks once all subblocks are unplugged. We can use the new Linux MM interface for that. As no memory is in use anymore, this shouldn't take a long time and shouldn't fail. There might be corner cases where the offlining could still fail (especially, if another notifier NACKs the offlining request).
Cc: "Michael S. Tsirkin" <[email protected]> Cc: Jason Wang <[email protected]> Cc: Oscar Salvador <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Igor Mammedov <[email protected]> Cc: Dave Young <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Dan Williams <[email protected]> Cc: Pavel Tatashin <[email protected]> Cc: Stefan Hajnoczi <[email protected]> Cc: Vlastimil Babka <[email protected]> Signed-off-by: David Hildenbrand <[email protected]> --- drivers/virtio/virtio_mem.c | 39 ++++++++++++++++++++++++++++++++++--- 1 file changed, 36 insertions(+), 3 deletions(-) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 9cb31459b211..01d5fc784d5d 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -433,6 +433,28 @@ static int virtio_mem_mb_remove(struct virtio_mem *vm, unsigned long mb_id) return remove_memory(nid, addr, memory_block_size_bytes()); } +/* + * Try to offline and remove a memory block from Linux. + * + * Must not be called with the vm->hotplug_mutex held (possible deadlock with + * onlining code). + * + * Will not modify the state of the memory block. + */ +static int virtio_mem_mb_offline_and_remove(struct virtio_mem *vm, + unsigned long mb_id) +{ + const uint64_t addr = virtio_mem_mb_id_to_phys(mb_id); + int nid = vm->nid; + + if (nid == NUMA_NO_NODE) + nid = memory_add_physaddr_to_nid(addr); + + dev_dbg(&vm->vdev->dev, "offlining and removing memory block: %lu\n", + mb_id); + return offline_and_remove_memory(nid, addr, memory_block_size_bytes()); +} + /* * Trigger the workqueue so the device can perform its magic. */ @@ -1263,7 +1285,8 @@ static int virtio_mem_mb_unplug_any_sb_offline(struct virtio_mem *vm, * Unplug the desired number of plugged subblocks of an online memory block. * Will skip subblock that are busy. * - * Will modify the state of the memory block. + * Will modify the state of the memory block. Might temporarily drop the + * hotplug_mutex. * * Note: Can fail after some subblocks were successfully unplugged. Can * return 0 even if subblocks were busy and could not get unplugged. @@ -1319,9 +1342,19 @@ static int virtio_mem_mb_unplug_any_sb_online(struct virtio_mem *vm, } /* - * TODO: Once all subblocks of a memory block were unplugged, we want - * to offline the memory block and remove it. + * Once all subblocks of a memory block were unplugged, offline and + * remove it. This will usually not fail, as no memory is in use + * anymore - however some other notifiers might NACK the request. */ + if (virtio_mem_mb_test_sb_unplugged(vm, mb_id, 0, vm->nb_sb_per_mb)) { + mutex_unlock(&vm->hotplug_mutex); + rc = virtio_mem_mb_offline_and_remove(vm, mb_id); + mutex_lock(&vm->hotplug_mutex); + if (!rc) + virtio_mem_mb_set_state(vm, mb_id, + VIRTIO_MEM_MB_STATE_UNUSED); + } + return 0; } -- 2.21.0
