qeth_get_elements_for_range() doesn't know how to handle a 0-length
range (ie. start == end), and returns 1 when it should return 0.
Such ranges occur on TSO skbs, where the L2/L3/L4 headers (and thus all
of the skb's linear data) are skipped when mapping the skb into regular
buffer elements.
This overestimation may cause several performance-related issues:
1. sub-optimal IO buffer selection, where the next buffer gets selected
even though the skb would actually still fit into the current buffer.
2. forced linearization, if the element count for a non-linear skb
exceeds QETH_MAX_BUFFER_ELEMENTS.
Rather than modifying qeth_get_elements_for_range() and adding overhead
to every caller, fix up those callers that are in risk of passing a
0-length range.
Fixes: 2863c61334aa ("qeth: refactor calculation of SBALE count")
Signed-off-by: Julian Wiedmann <j...@linux.vnet.ibm.com>
---
drivers/s390/net/qeth_core_main.c | 10 ++++++----
drivers/s390/net/qeth_l3_main.c | 11 ++++++-----
2 files changed, 12 insertions(+), 9 deletions(-)
diff --git a/drivers/s390/net/qeth_core_main.c
b/drivers/s390/net/qeth_core_main.c
index ca72f3311004..30457fca30c5 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -3898,10 +3898,12 @@ EXPORT_SYMBOL_GPL(qeth_get_elements_for_frags);
int qeth_get_elements_no(struct qeth_card *card,
struct sk_buff *skb, int extra_elems, int data_offset)
{
- int elements = qeth_get_elements_for_range(
- (addr_t)skb->data + data_offset,
- (addr_t)skb->data + skb_headlen(skb)) +
- qeth_get_elements_for_frags(skb);
+ addr_t end = (addr_t)skb->data + skb_headlen(skb);
+ int elements = qeth_get_elements_for_frags(skb);
+ addr_t start = (addr_t)skb->data + data_offset;
+
+ if (start != end)
+ elements += qeth_get_elements_for_range(start, end);
if ((elements + extra_elems) > QETH_MAX_BUFFER_ELEMENTS(card)) {
QETH_DBF_MESSAGE(2, "Invalid size of IP packet "
diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index b0c888e86cd4..3421893c37a4 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -2450,11 +2450,12 @@ static void qeth_tso_fill_header(struct qeth_card *card,
static int qeth_l3_get_elements_no_tso(struct qeth_card *card,
struct sk_buff *skb, int extra_elems)
{
- addr_t tcpdptr = (addr_t)tcp_hdr(skb) + tcp_hdrlen(skb);
- int elements = qeth_get_elements_for_range(
- tcpdptr,
- (addr_t)skb->data + skb_headlen(skb)) +
- qeth_get_elements_for_frags(skb);
+ addr_t start = (addr_t)tcp_hdr(skb) + tcp_hdrlen(skb);
+ addr_t end = (addr_t)skb->data + skb_headlen(skb);
+ int elements = qeth_get_elements_for_frags(skb);
+
+ if (start != end)
+ elements += qeth_get_elements_for_range(start, end);
if ((elements + extra_elems) > QETH_MAX_BUFFER_ELEMENTS(card)) {
QETH_DBF_MESSAGE(2,
--
2.13.5
