Patch "net: qed: fix left elements count calculation" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: qed: fix left elements count calculation

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-qed-fix-left-elements-count-calculation.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 16cb39a9af4637f731754365f461710da6d966fc
Author: Alexander Lobakin <alobakin@xxxxxxxxxxx>
Date:   Tue Jun 23 16:51:29 2020 +0300

    net: qed: fix left elements count calculation
    
    [ Upstream commit 97dd1abd026ae4e6a82fa68645928404ad483409 ]
    
    qed_chain_get_element_left{,_u32} returned 0 when the difference
    between producer and consumer page count was equal to the total
    page count.
    Fix this by conditional expanding of producer value (vs
    unconditional). This allowed to eliminate normalizaton against
    total page count, which was the cause of this bug.
    
    Misc: replace open-coded constants with common defines.
    
    Fixes: a91eb52abb50 ("qed: Revisit chain implementation")
    Signed-off-by: Alexander Lobakin <alobakin@xxxxxxxxxxx>
    Signed-off-by: Igor Russkikh <irusskikh@xxxxxxxxxxx>
    Signed-off-by: Michal Kalderon <michal.kalderon@xxxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/qed/qed_chain.h b/include/linux/qed/qed_chain.h
index 733fad7dfbed9..6d15040c642cb 100644
--- a/include/linux/qed/qed_chain.h
+++ b/include/linux/qed/qed_chain.h
@@ -207,28 +207,34 @@ static inline u32 qed_chain_get_cons_idx_u32(struct qed_chain *p_chain)
 
 static inline u16 qed_chain_get_elem_left(struct qed_chain *p_chain)
 {
+	u16 elem_per_page = p_chain->elem_per_page;
+	u32 prod = p_chain->u.chain16.prod_idx;
+	u32 cons = p_chain->u.chain16.cons_idx;
 	u16 used;
 
-	used = (u16) (((u32)0x10000 +
-		       (u32)p_chain->u.chain16.prod_idx) -
-		      (u32)p_chain->u.chain16.cons_idx);
+	if (prod < cons)
+		prod += (u32)U16_MAX + 1;
+
+	used = (u16)(prod - cons);
 	if (p_chain->mode == QED_CHAIN_MODE_NEXT_PTR)
-		used -= p_chain->u.chain16.prod_idx / p_chain->elem_per_page -
-		    p_chain->u.chain16.cons_idx / p_chain->elem_per_page;
+		used -= prod / elem_per_page - cons / elem_per_page;
 
 	return (u16)(p_chain->capacity - used);
 }
 
 static inline u32 qed_chain_get_elem_left_u32(struct qed_chain *p_chain)
 {
+	u16 elem_per_page = p_chain->elem_per_page;
+	u64 prod = p_chain->u.chain32.prod_idx;
+	u64 cons = p_chain->u.chain32.cons_idx;
 	u32 used;
 
-	used = (u32) (((u64)0x100000000ULL +
-		       (u64)p_chain->u.chain32.prod_idx) -
-		      (u64)p_chain->u.chain32.cons_idx);
+	if (prod < cons)
+		prod += (u64)U32_MAX + 1;
+
+	used = (u32)(prod - cons);
 	if (p_chain->mode == QED_CHAIN_MODE_NEXT_PTR)
-		used -= p_chain->u.chain32.prod_idx / p_chain->elem_per_page -
-		    p_chain->u.chain32.cons_idx / p_chain->elem_per_page;
+		used -= (u32)(prod / elem_per_page - cons / elem_per_page);
 
 	return p_chain->capacity - used;
 }