qed: Fix corner case for chain in-between pages

The amount of chain next pointer elements between the producer
and the consumer indices depends on which pages they currently
point to. The current calculation is based only on their difference,
and it can lead to a number of free elements which is higher by 1
than the actual value.

Signed-off-by: Tomer Tayar <Tomer.Tayar@qlogic.com>
Signed-off-by: Manish Chopra <manish.chopra@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Orabug: 23732603
Signed-off-by: Manjunath Govindashetty <manjunath.govindashetty@oracle.com>

diff --git a/include/linux/qed/qed_chain.h b/include/linux/qed/qed_chain.h
index b920c3605c462ef0bdb9c8ba0c8cd9d8957addb7..41b9049b57e2475575d076b4f0728234618ce07e 100644 (file)
--- a/include/linux/qed/qed_chain.h
+++ b/include/linux/qed/qed_chain.h
@@ -111,7 +111,8 @@ static inline u16 qed_chain_get_elem_left(struct qed_chain *p_chain)
        used = ((u32)0x10000u + (u32)(p_chain->prod_idx)) -
                (u32)p_chain->cons_idx;
        if (p_chain->mode == QED_CHAIN_MODE_NEXT_PTR)
-               used -= (used / p_chain->elem_per_page);
+               used -= p_chain->prod_idx / p_chain->elem_per_page -
+                       p_chain->cons_idx / p_chain->elem_per_page;
 
        return p_chain->capacity - used;
 }