tcmu: fix free block calculation

Web:        https://git.kernel.org/torvalds/c/3c0f26ff9d040c6193b33689bbc03103854dba4d
Commit:     3c0f26ff9d040c6193b33689bbc03103854dba4d
Parent:     1a1fc0b88e9019cb3b2f291bdcb2d03d38614690
Refname:    refs/heads/master
Author:     Mike Christie <[email protected]>
AuthorDate: Tue Nov 28 12:40:35 2017 -0600
Committer:  Nicholas Bellinger <[email protected]>
CommitDate: Fri Jan 12 15:07:16 2018 -0800

    tcmu: fix free block calculation
    
    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 <[email protected]>
    Signed-off-by: Nicholas Bellinger <[email protected]>
---
 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 965f462eaa22..5d1daea51079 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -637,7 +637,7 @@ 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);
 }
 
 /*
@@ -677,8 +677,9 @@ 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) {
--
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