[PATCH 15/20] tcmu: fix free block calculation

[Mike Christie <mchristi@redhat.com>]

The blocks_left calculation does not account for free blocks
between 0 and thresh, so we could be queueing/waiting when
there are enough blocks free.

This has us add in the blocks between 0 and thresh as well as
at the end from thresh to DATA_BLOCK_BITS.

Signed-off-by: Mike Christie <mchristi@redhat.com>
---
 drivers/target/target_core_user.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 45cf37f..5eb919a 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -675,7 +675,7 @@ static void gather_data_area(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
 
 static inline size_t spc_bitmap_free(unsigned long *bitmap, uint32_t thresh)
 {
-	return DATA_BLOCK_SIZE * (thresh - bitmap_weight(bitmap, thresh));
+	return thresh - bitmap_weight(bitmap, thresh);
 }
 
 /*
@@ -715,8 +715,9 @@ static bool is_ring_space_avail(struct tcmu_dev *udev, struct tcmu_cmd *cmd,
 
 	/* try to check and get the data blocks as needed */
 	space = spc_bitmap_free(udev->data_bitmap, udev->dbi_thresh);
-	if (space < data_needed) {
-		unsigned long blocks_left = DATA_BLOCK_BITS - udev->dbi_thresh;
+	if ((space * DATA_BLOCK_SIZE) < data_needed) {
+		unsigned long blocks_left = DATA_BLOCK_BITS - udev->dbi_thresh +
+						space;
 		unsigned long grow;
 
 		if (blocks_left < blocks_needed) {
-- 
2.7.2