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Date:   Fri, 16 Oct 2020 16:43:10 +0800
From:   Wei Yang <richard.weiyang@...ux.alibaba.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        virtualization@...ts.linux-foundation.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>
Subject: Re: [PATCH v1 17/29] virito-mem: subblock states are specific to Sub
 Block Mode (SBM)

On Mon, Oct 12, 2020 at 02:53:11PM +0200, David Hildenbrand wrote:
>Let's rename and move accordingly. While at it, rename sb_bitmap to
>"sb_states".
>
>Cc: "Michael S. Tsirkin" <mst@...hat.com>
>Cc: Jason Wang <jasowang@...hat.com>
>Cc: Pankaj Gupta <pankaj.gupta.linux@...il.com>
>Signed-off-by: David Hildenbrand <david@...hat.com>

Ok, you separate the change into two parts.

Reviewed-by: Wei Yang <richard.weiyang@...ux.alibaba.com>

>---
> drivers/virtio/virtio_mem.c | 118 +++++++++++++++++++-----------------
> 1 file changed, 62 insertions(+), 56 deletions(-)
>
>diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
>index e76d6f769aa5..2cc497ad8298 100644
>--- a/drivers/virtio/virtio_mem.c
>+++ b/drivers/virtio/virtio_mem.c
>@@ -137,17 +137,23 @@ struct virtio_mem {
> 		 * memory in one 4 KiB page.
> 		 */
> 		uint8_t *mb_states;
>-	} sbm;
> 
>-	/*
>-	 * $nb_sb_per_mb bit per memory block. Handled similar to sbm.mb_states.
>-	 *
>-	 * With 4MB subblocks, we manage 128GB of memory in one page.
>-	 */
>-	unsigned long *sb_bitmap;
>+		/*
>+		 * Bitmap: one bit per subblock. Allocated similar to
>+		 * sbm.mb_states.
>+		 *
>+		 * A set bit means the corresponding subblock is plugged,
>+		 * otherwise it's unblocked.
>+		 *
>+		 * With 4 MiB subblocks, we manage 128 GiB of memory in one
>+		 * 4 KiB page.
>+		 */
>+		unsigned long *sb_states;
>+	} sbm;
> 
> 	/*
>-	 * Mutex that protects the sbm.mb_count, sbm.mb_states, and sb_bitmap.
>+	 * Mutex that protects the sbm.mb_count, sbm.mb_states, and
>+	 * sbm.sb_states.
> 	 *
> 	 * When this lock is held the pointers can't change, ONLINE and
> 	 * OFFLINE blocks can't change the state and no subblocks will get
>@@ -326,13 +332,13 @@ static int virtio_mem_sbm_mb_states_prepare_next_mb(struct virtio_mem *vm)
>  *
>  * Will not modify the state of the memory block.
>  */
>-static void virtio_mem_mb_set_sb_plugged(struct virtio_mem *vm,
>-					 unsigned long mb_id, int sb_id,
>-					 int count)
>+static void virtio_mem_sbm_set_sb_plugged(struct virtio_mem *vm,
>+					  unsigned long mb_id, int sb_id,
>+					  int count)
> {
> 	const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
> 
>-	__bitmap_set(vm->sb_bitmap, bit, count);
>+	__bitmap_set(vm->sbm.sb_states, bit, count);
> }
> 
> /*
>@@ -340,86 +346,87 @@ static void virtio_mem_mb_set_sb_plugged(struct virtio_mem *vm,
>  *
>  * Will not modify the state of the memory block.
>  */
>-static void virtio_mem_mb_set_sb_unplugged(struct virtio_mem *vm,
>-					   unsigned long mb_id, int sb_id,
>-					   int count)
>+static void virtio_mem_sbm_set_sb_unplugged(struct virtio_mem *vm,
>+					    unsigned long mb_id, int sb_id,
>+					    int count)
> {
> 	const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
> 
>-	__bitmap_clear(vm->sb_bitmap, bit, count);
>+	__bitmap_clear(vm->sbm.sb_states, bit, count);
> }
> 
> /*
>  * Test if all selected subblocks are plugged.
>  */
>-static bool virtio_mem_mb_test_sb_plugged(struct virtio_mem *vm,
>-					  unsigned long mb_id, int sb_id,
>-					  int count)
>+static bool virtio_mem_sbm_test_sb_plugged(struct virtio_mem *vm,
>+					   unsigned long mb_id, int sb_id,
>+					   int count)
> {
> 	const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
> 
> 	if (count == 1)
>-		return test_bit(bit, vm->sb_bitmap);
>+		return test_bit(bit, vm->sbm.sb_states);
> 
> 	/* TODO: Helper similar to bitmap_set() */
>-	return find_next_zero_bit(vm->sb_bitmap, bit + count, bit) >=
>+	return find_next_zero_bit(vm->sbm.sb_states, bit + count, bit) >=
> 	       bit + count;
> }
> 
> /*
>  * Test if all selected subblocks are unplugged.
>  */
>-static bool virtio_mem_mb_test_sb_unplugged(struct virtio_mem *vm,
>-					    unsigned long mb_id, int sb_id,
>-					    int count)
>+static bool virtio_mem_sbm_test_sb_unplugged(struct virtio_mem *vm,
>+					     unsigned long mb_id, int sb_id,
>+					     int count)
> {
> 	const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
> 
> 	/* TODO: Helper similar to bitmap_set() */
>-	return find_next_bit(vm->sb_bitmap, bit + count, bit) >= bit + count;
>+	return find_next_bit(vm->sbm.sb_states, bit + count, bit) >=
>+	       bit + count;
> }
> 
> /*
>  * Find the first unplugged subblock. Returns vm->nb_sb_per_mb in case there is
>  * none.
>  */
>-static int virtio_mem_mb_first_unplugged_sb(struct virtio_mem *vm,
>+static int virtio_mem_sbm_first_unplugged_sb(struct virtio_mem *vm,
> 					    unsigned long mb_id)
> {
> 	const int bit = (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb;
> 
>-	return find_next_zero_bit(vm->sb_bitmap, bit + vm->nb_sb_per_mb, bit) -
>-	       bit;
>+	return find_next_zero_bit(vm->sbm.sb_states,
>+				  bit + vm->nb_sb_per_mb, bit) - bit;
> }
> 
> /*
>  * Prepare the subblock bitmap for the next memory block.
>  */
>-static int virtio_mem_sb_bitmap_prepare_next_mb(struct virtio_mem *vm)
>+static int virtio_mem_sbm_sb_states_prepare_next_mb(struct virtio_mem *vm)
> {
> 	const unsigned long old_nb_mb = vm->next_mb_id - vm->first_mb_id;
> 	const unsigned long old_nb_bits = old_nb_mb * vm->nb_sb_per_mb;
> 	const unsigned long new_nb_bits = (old_nb_mb + 1) * vm->nb_sb_per_mb;
> 	int old_pages = PFN_UP(BITS_TO_LONGS(old_nb_bits) * sizeof(long));
> 	int new_pages = PFN_UP(BITS_TO_LONGS(new_nb_bits) * sizeof(long));
>-	unsigned long *new_sb_bitmap, *old_sb_bitmap;
>+	unsigned long *new_bitmap, *old_bitmap;
> 
>-	if (vm->sb_bitmap && old_pages == new_pages)
>+	if (vm->sbm.sb_states && old_pages == new_pages)
> 		return 0;
> 
>-	new_sb_bitmap = vzalloc(new_pages * PAGE_SIZE);
>-	if (!new_sb_bitmap)
>+	new_bitmap = vzalloc(new_pages * PAGE_SIZE);
>+	if (!new_bitmap)
> 		return -ENOMEM;
> 
> 	mutex_lock(&vm->hotplug_mutex);
>-	if (new_sb_bitmap)
>-		memcpy(new_sb_bitmap, vm->sb_bitmap, old_pages * PAGE_SIZE);
>+	if (new_bitmap)
>+		memcpy(new_bitmap, vm->sbm.sb_states, old_pages * PAGE_SIZE);
> 
>-	old_sb_bitmap = vm->sb_bitmap;
>-	vm->sb_bitmap = new_sb_bitmap;
>+	old_bitmap = vm->sbm.sb_states;
>+	vm->sbm.sb_states = new_bitmap;
> 	mutex_unlock(&vm->hotplug_mutex);
> 
>-	vfree(old_sb_bitmap);
>+	vfree(old_bitmap);
> 	return 0;
> }
> 
>@@ -630,7 +637,7 @@ static void virtio_mem_notify_going_offline(struct virtio_mem *vm,
> 	int sb_id;
> 
> 	for (sb_id = 0; sb_id < vm->nb_sb_per_mb; sb_id++) {
>-		if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
>+		if (virtio_mem_sbm_test_sb_plugged(vm, mb_id, sb_id, 1))
> 			continue;
> 		pfn = PFN_DOWN(virtio_mem_mb_id_to_phys(mb_id) +
> 			       sb_id * vm->subblock_size);
>@@ -646,7 +653,7 @@ static void virtio_mem_notify_cancel_offline(struct virtio_mem *vm,
> 	int sb_id;
> 
> 	for (sb_id = 0; sb_id < vm->nb_sb_per_mb; sb_id++) {
>-		if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
>+		if (virtio_mem_sbm_test_sb_plugged(vm, mb_id, sb_id, 1))
> 			continue;
> 		pfn = PFN_DOWN(virtio_mem_mb_id_to_phys(mb_id) +
> 			       sb_id * vm->subblock_size);
>@@ -936,7 +943,7 @@ static void virtio_mem_online_page_cb(struct page *page, unsigned int order)
> 		 * If plugged, online the pages, otherwise, set them fake
> 		 * offline (PageOffline).
> 		 */
>-		if (virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
>+		if (virtio_mem_sbm_test_sb_plugged(vm, mb_id, sb_id, 1))
> 			generic_online_page(page, order);
> 		else
> 			virtio_mem_set_fake_offline(PFN_DOWN(addr), 1 << order,
>@@ -1071,7 +1078,7 @@ static int virtio_mem_mb_plug_sb(struct virtio_mem *vm, unsigned long mb_id,
> 
> 	rc = virtio_mem_send_plug_request(vm, addr, size);
> 	if (!rc)
>-		virtio_mem_mb_set_sb_plugged(vm, mb_id, sb_id, count);
>+		virtio_mem_sbm_set_sb_plugged(vm, mb_id, sb_id, count);
> 	return rc;
> }
> 
>@@ -1092,7 +1099,7 @@ static int virtio_mem_mb_unplug_sb(struct virtio_mem *vm, unsigned long mb_id,
> 
> 	rc = virtio_mem_send_unplug_request(vm, addr, size);
> 	if (!rc)
>-		virtio_mem_mb_set_sb_unplugged(vm, mb_id, sb_id, count);
>+		virtio_mem_sbm_set_sb_unplugged(vm, mb_id, sb_id, count);
> 	return rc;
> }
> 
>@@ -1115,14 +1122,14 @@ static int virtio_mem_mb_unplug_any_sb(struct virtio_mem *vm,
> 	while (*nb_sb) {
> 		/* Find the next candidate subblock */
> 		while (sb_id >= 0 &&
>-		       virtio_mem_mb_test_sb_unplugged(vm, mb_id, sb_id, 1))
>+		       virtio_mem_sbm_test_sb_unplugged(vm, mb_id, sb_id, 1))
> 			sb_id--;
> 		if (sb_id < 0)
> 			break;
> 		/* Try to unplug multiple subblocks at a time */
> 		count = 1;
> 		while (count < *nb_sb && sb_id > 0 &&
>-		       virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id - 1, 1)) {
>+		       virtio_mem_sbm_test_sb_plugged(vm, mb_id, sb_id - 1, 1)) {
> 			count++;
> 			sb_id--;
> 		}
>@@ -1168,7 +1175,7 @@ static int virtio_mem_prepare_next_mb(struct virtio_mem *vm,
> 		return rc;
> 
> 	/* Resize the subblock bitmap if required. */
>-	rc = virtio_mem_sb_bitmap_prepare_next_mb(vm);
>+	rc = virtio_mem_sbm_sb_states_prepare_next_mb(vm);
> 	if (rc)
> 		return rc;
> 
>@@ -1253,14 +1260,13 @@ static int virtio_mem_mb_plug_any_sb(struct virtio_mem *vm, unsigned long mb_id,
> 		return -EINVAL;
> 
> 	while (*nb_sb) {
>-		sb_id = virtio_mem_mb_first_unplugged_sb(vm, mb_id);
>+		sb_id = virtio_mem_sbm_first_unplugged_sb(vm, mb_id);
> 		if (sb_id >= vm->nb_sb_per_mb)
> 			break;
> 		count = 1;
> 		while (count < *nb_sb &&
> 		       sb_id + count < vm->nb_sb_per_mb &&
>-		       !virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id + count,
>-						      1))
>+		       !virtio_mem_sbm_test_sb_plugged(vm, mb_id, sb_id + count, 1))
> 			count++;
> 
> 		rc = virtio_mem_mb_plug_sb(vm, mb_id, sb_id, count);
>@@ -1277,7 +1283,7 @@ static int virtio_mem_mb_plug_any_sb(struct virtio_mem *vm, unsigned long mb_id,
> 		virtio_mem_fake_online(pfn, nr_pages);
> 	}
> 
>-	if (virtio_mem_mb_test_sb_plugged(vm, mb_id, 0, vm->nb_sb_per_mb)) {
>+	if (virtio_mem_sbm_test_sb_plugged(vm, mb_id, 0, vm->nb_sb_per_mb)) {
> 		if (online)
> 			virtio_mem_sbm_set_mb_state(vm, mb_id,
> 						    VIRTIO_MEM_SBM_MB_ONLINE);
>@@ -1377,13 +1383,13 @@ static int virtio_mem_mb_unplug_any_sb_offline(struct virtio_mem *vm,
> 	rc = virtio_mem_mb_unplug_any_sb(vm, mb_id, nb_sb);
> 
> 	/* some subblocks might have been unplugged even on failure */
>-	if (!virtio_mem_mb_test_sb_plugged(vm, mb_id, 0, vm->nb_sb_per_mb))
>+	if (!virtio_mem_sbm_test_sb_plugged(vm, mb_id, 0, vm->nb_sb_per_mb))
> 		virtio_mem_sbm_set_mb_state(vm, mb_id,
> 					    VIRTIO_MEM_SBM_MB_OFFLINE_PARTIAL);
> 	if (rc)
> 		return rc;
> 
>-	if (virtio_mem_mb_test_sb_unplugged(vm, mb_id, 0, vm->nb_sb_per_mb)) {
>+	if (virtio_mem_sbm_test_sb_unplugged(vm, mb_id, 0, vm->nb_sb_per_mb)) {
> 		/*
> 		 * Remove the block from Linux - this should never fail.
> 		 * Hinder the block from getting onlined by marking it
>@@ -1452,7 +1458,7 @@ static int virtio_mem_mb_unplug_any_sb_online(struct virtio_mem *vm,
> 
> 	/* If possible, try to unplug the complete block in one shot. */
> 	if (*nb_sb >= vm->nb_sb_per_mb &&
>-	    virtio_mem_mb_test_sb_plugged(vm, mb_id, 0, vm->nb_sb_per_mb)) {
>+	    virtio_mem_sbm_test_sb_plugged(vm, mb_id, 0, vm->nb_sb_per_mb)) {
> 		rc = virtio_mem_mb_unplug_sb_online(vm, mb_id, 0,
> 						    vm->nb_sb_per_mb);
> 		if (!rc) {
>@@ -1466,7 +1472,7 @@ static int virtio_mem_mb_unplug_any_sb_online(struct virtio_mem *vm,
> 	for (sb_id = vm->nb_sb_per_mb - 1; sb_id >= 0 && *nb_sb; sb_id--) {
> 		/* Find the next candidate subblock */
> 		while (sb_id >= 0 &&
>-		       !virtio_mem_mb_test_sb_plugged(vm, mb_id, sb_id, 1))
>+		       !virtio_mem_sbm_test_sb_plugged(vm, mb_id, sb_id, 1))
> 			sb_id--;
> 		if (sb_id < 0)
> 			break;
>@@ -1485,7 +1491,7 @@ static int virtio_mem_mb_unplug_any_sb_online(struct virtio_mem *vm,
> 	 * 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)) {
>+	if (virtio_mem_sbm_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);
>@@ -2007,7 +2013,7 @@ static void virtio_mem_remove(struct virtio_device *vdev)
> 
> 	/* remove all tracking data - no locking needed */
> 	vfree(vm->sbm.mb_states);
>-	vfree(vm->sb_bitmap);
>+	vfree(vm->sbm.sb_states);
> 
> 	/* reset the device and cleanup the queues */
> 	vdev->config->reset(vdev);
>-- 
>2.26.2

-- 
Wei Yang
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