Commit c6bc1422 authored by David Hildenbrand's avatar David Hildenbrand Committed by Michael S. Tsirkin
Browse files

virtio-mem: simplify high-level unplug handling in Big Block Mode 



Let's simplify high-level big block selection when unplugging in
Big Block Mode.

Combine handling of offline and online blocks. We can get rid of
virtio_mem_bbm_bb_is_offline() and simply use
virtio_mem_bbm_offline_remove_and_unplug_bb(), as that already tolerates
offline parts.

We can race with concurrent onlining/offlining either way, so we don;t
have to be super correct by failing if an offline big block we'd like to
unplug just got (partially) onlined.

Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20210602185720.31821-7-david@redhat.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent c740bb97

drivers/virtio/virtio_mem.c

+24 −72
Original line number Diff line number Diff line
@@ -702,18 +702,6 @@ static int virtio_mem_sbm_remove_mb(struct virtio_mem *vm, unsigned long mb_id) 
	return virtio_mem_remove_memory(vm, addr, size);

}



/*

 * See virtio_mem_remove_memory(): Try to remove all Linux memory blocks covered

 * by the big block.

 */

static int virtio_mem_bbm_remove_bb(struct virtio_mem *vm, unsigned long bb_id)

{

	const uint64_t addr = virtio_mem_bb_id_to_phys(vm, bb_id);

	const uint64_t size = vm->bbm.bb_size;



	return virtio_mem_remove_memory(vm, addr, size);

}



/*

 * Try offlining and removing memory from Linux.

 *
@@ -2114,35 +2102,6 @@ static int virtio_mem_bbm_offline_remove_and_unplug_bb(struct virtio_mem *vm, 
	return rc;

}



/*

 * Try to remove a big block from Linux and unplug it. Will fail with

 * -EBUSY if some memory is online.

 *

 * Will modify the state of the memory block.

 */

static int virtio_mem_bbm_remove_and_unplug_bb(struct virtio_mem *vm,

					       unsigned long bb_id)

{

	int rc;



	if (WARN_ON_ONCE(virtio_mem_bbm_get_bb_state(vm, bb_id) !=

			 VIRTIO_MEM_BBM_BB_ADDED))

		return -EINVAL;



	rc = virtio_mem_bbm_remove_bb(vm, bb_id);

	if (rc)

		return -EBUSY;



	rc = virtio_mem_bbm_unplug_bb(vm, bb_id);

	if (rc)

		virtio_mem_bbm_set_bb_state(vm, bb_id,

					    VIRTIO_MEM_BBM_BB_PLUGGED);

	else

		virtio_mem_bbm_set_bb_state(vm, bb_id,

					    VIRTIO_MEM_BBM_BB_UNUSED);

	return rc;

}



/*

 * Test if a big block is completely offline.

 */
@@ -2166,21 +2125,26 @@ static int virtio_mem_bbm_unplug_request(struct virtio_mem *vm, uint64_t diff) 
{

	uint64_t nb_bb = diff / vm->bbm.bb_size;

	uint64_t bb_id;

	int rc;

	int rc, i;



	if (!nb_bb)

		return 0;



	/* Try to unplug completely offline big blocks first. */

	/*

	 * Try to unplug big blocks. Similar to SBM, start with offline

	 * big blocks.

	 */

	for (i = 0; i < 2; i++) {

		virtio_mem_bbm_for_each_bb_rev(vm, bb_id, VIRTIO_MEM_BBM_BB_ADDED) {

			cond_resched();



			/*

		 * As we're holding no locks, this check is racy as memory

		 * can get onlined in the meantime - but we'll fail gracefully.

			 * As we're holding no locks, these checks are racy,

			 * but we don't care.

			 */

		if (!virtio_mem_bbm_bb_is_offline(vm, bb_id))

			if (i == 0 && !virtio_mem_bbm_bb_is_offline(vm, bb_id))

				continue;

		rc = virtio_mem_bbm_remove_and_unplug_bb(vm, bb_id);

			rc = virtio_mem_bbm_offline_remove_and_unplug_bb(vm, bb_id);

			if (rc == -EBUSY)

				continue;

			if (!rc)
@@ -2188,20 +2152,8 @@ static int virtio_mem_bbm_unplug_request(struct virtio_mem *vm, uint64_t diff) 
			if (rc || !nb_bb)

				return rc;

		}



	if (!unplug_online)

		if (i == 0 && !unplug_online)

			return 0;



	/* Try to unplug any big blocks. */

	virtio_mem_bbm_for_each_bb_rev(vm, bb_id, VIRTIO_MEM_BBM_BB_ADDED) {

		cond_resched();

		rc = virtio_mem_bbm_offline_remove_and_unplug_bb(vm, bb_id);

		if (rc == -EBUSY)

			continue;

		if (!rc)

			nb_bb--;

		if (rc || !nb_bb)

			return rc;

	}



	return nb_bb ? -EBUSY : 0;