[PATCH v1 18/29] virtio-mem: factor out calculation of the bit number within the sb_states bitmap

[David Hildenbrand <david@xxxxxxxxxx>]

The calculation is already complicated enough, let's limit it to one
location.

Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 drivers/virtio/virtio_mem.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 2cc497ad8298..73ff6e9ba839 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -327,6 +327,16 @@ static int virtio_mem_sbm_mb_states_prepare_next_mb(struct virtio_mem *vm)
 	     _mb_id--) \
 		if (virtio_mem_sbm_get_mb_state(_vm, _mb_id) == _state)
 
+/*
+ * Calculate the bit number in the sb_states bitmap for the given subblock
+ * inside the given memory block.
+ */
+static int virtio_mem_sbm_sb_state_bit_nr(struct virtio_mem *vm,
+					  unsigned long mb_id, int sb_id)
+{
+	return (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id;
+}
+
 /*
  * Mark all selected subblocks plugged.
  *
@@ -336,7 +346,7 @@ 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;
+	const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, sb_id);
 
 	__bitmap_set(vm->sbm.sb_states, bit, count);
 }
@@ -350,7 +360,7 @@ 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;
+	const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, sb_id);
 
 	__bitmap_clear(vm->sbm.sb_states, bit, count);
 }
@@ -362,7 +372,7 @@ 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;
+	const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, sb_id);
 
 	if (count == 1)
 		return test_bit(bit, vm->sbm.sb_states);
@@ -379,7 +389,7 @@ 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;
+	const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, sb_id);
 
 	/* TODO: Helper similar to bitmap_set() */
 	return find_next_bit(vm->sbm.sb_states, bit + count, bit) >=
@@ -393,7 +403,7 @@ static bool virtio_mem_sbm_test_sb_unplugged(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;
+	const int bit = virtio_mem_sbm_sb_state_bit_nr(vm, mb_id, 0);
 
 	return find_next_zero_bit(vm->sbm.sb_states,
 				  bit + vm->nb_sb_per_mb, bit) - bit;
-- 
2.26.2