qeth: refactor calculation of SBALE count

Rewrite the functions that calculate the required number of buffer
elements needed to represent SKB data, to make them hopefully more
comprehensible. Plus a few cleanups.

Signed-off-by: Eugene Crosser <Eugene.Crosser@ru.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 85 insertions, 41 deletions

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index ec2e014e885c..eb8f434a2681 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -844,6 +844,19 @@ struct qeth_trap_id {
 /*some helper functions*/
 #define QETH_CARD_IFNAME(card) (((card)->dev)? (card)->dev->name : "")
 
+/**
+ * qeth_get_elements_for_range() -      find number of SBALEs to cover range.
+ * @start:                              Start of the address range.
+ * @end:                                Address after the end of the range.
+ *
+ * Returns the number of pages, and thus QDIO buffer elements, needed to cover
+ * the specified address range.
+ */
+static inline int qeth_get_elements_for_range(addr_t start, addr_t end)
+{
+        return PFN_UP(end - 1) - PFN_DOWN(start);
+}
+
 static inline int qeth_get_micros(void)
 {
         return (int) (get_tod_clock() >> 12);
diff --git a/drivers/s390/net/qeth_core_main.c b/drivers/s390/net/qeth_core_main.c
index b7b74776e2ff..a91a31d2fc9a 100644
--- a/drivers/s390/net/qeth_core_main.c
+++ b/drivers/s390/net/qeth_core_main.c
@@ -3810,41 +3810,54 @@ int qeth_get_priority_queue(struct qeth_card *card, struct sk_buff *skb,
 }
 EXPORT_SYMBOL_GPL(qeth_get_priority_queue);
 
+/**
+ * qeth_get_elements_for_frags() -      find number of SBALEs for skb frags.
+ * @skb:                                SKB address
+ *
+ * Returns the number of pages, and thus QDIO buffer elements, needed to cover
+ * fragmented part of the SKB. Returns zero for linear SKB.
+ */
 int qeth_get_elements_for_frags(struct sk_buff *skb)
 {
-        int cnt, length, e, elements = 0;
-        struct skb_frag_struct *frag;
-        char *data;
+        int cnt, elements = 0;
 
         for (cnt = 0; cnt < skb_shinfo(skb)->nr_frags; cnt++) {
-                frag = &skb_shinfo(skb)->frags[cnt];
-                data = (char *)page_to_phys(skb_frag_page(frag)) +
-                        frag->page_offset;
-                length = frag->size;
-                e = PFN_UP((unsigned long)data + length - 1) -
-                        PFN_DOWN((unsigned long)data);
-                elements += e;
+                struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[cnt];
+
+                elements += qeth_get_elements_for_range(
+                        (addr_t)skb_frag_address(frag),
+                        (addr_t)skb_frag_address(frag) + skb_frag_size(frag));
         }
         return elements;
 }
 EXPORT_SYMBOL_GPL(qeth_get_elements_for_frags);
 
+/**
+ * qeth_get_elements_no() -     find number of SBALEs for skb data, inc. frags.
+ * @card:                       qeth card structure, to check max. elems.
+ * @skb:                        SKB address
+ * @extra_elems:                extra elems needed, to check against max.
+ *
+ * Returns the number of pages, and thus QDIO buffer elements, needed to cover
+ * skb data, including linear part and fragments. Checks if the result plus
+ * extra_elems fits under the limit for the card. Returns 0 if it does not.
+ * Note: extra_elems is not included in the returned result.
+ */
 int qeth_get_elements_no(struct qeth_card *card,
-                     struct sk_buff *skb, int elems)
+                     struct sk_buff *skb, int extra_elems)
 {
-        int dlen = skb->len - skb->data_len;
-        int elements_needed = PFN_UP((unsigned long)skb->data + dlen - 1) -
-                PFN_DOWN((unsigned long)skb->data);
-
-        elements_needed += qeth_get_elements_for_frags(skb);
+        int elements = qeth_get_elements_for_range(
+                                (addr_t)skb->data,
+                                (addr_t)skb->data + skb_headlen(skb)) +
+                        qeth_get_elements_for_frags(skb);
 
-        if ((elements_needed + elems) > QETH_MAX_BUFFER_ELEMENTS(card)) {
+        if ((elements + extra_elems) > QETH_MAX_BUFFER_ELEMENTS(card)) {
                 QETH_DBF_MESSAGE(2, "Invalid size of IP packet "
                         "(Number=%d / Length=%d). Discarded.\n",
-                        (elements_needed+elems), skb->len);
+                        elements + extra_elems, skb->len);
                 return 0;
         }
-        return elements_needed;
+        return elements;
 }
 EXPORT_SYMBOL_GPL(qeth_get_elements_no);
 
@@ -3859,7 +3872,7 @@ int qeth_hdr_chk_and_bounce(struct sk_buff *skb, struct qeth_hdr **hdr, int len)
                 rest = len - inpage;
                 if (rest > hroom)
                         return 1;
-                memmove(skb->data - rest, skb->data, skb->len - skb->data_len);
+                memmove(skb->data - rest, skb->data, skb_headlen(skb));
                 skb->data -= rest;
                 skb->tail -= rest;
                 *hdr = (struct qeth_hdr *)skb->data;
@@ -3873,7 +3886,7 @@ static inline void __qeth_fill_buffer(struct sk_buff *skb,
         struct qdio_buffer *buffer, int is_tso, int *next_element_to_fill,
         int offset)
 {
-        int length = skb->len - skb->data_len;
+        int length = skb_headlen(skb);
         int length_here;
         int element;
         char *data;
diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index ac544330daeb..7c9968adb66d 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -2793,15 +2793,34 @@ static void qeth_tso_fill_header(struct qeth_card *card,
         }
 }
 
-static inline int qeth_l3_tso_elements(struct sk_buff *skb)
+/**
+ * qeth_get_elements_no_tso() - find number of SBALEs for skb data, inc. frags.
+ * @card:                       qeth card structure, to check max. elems.
+ * @skb:                        SKB address
+ * @extra_elems:                extra elems needed, to check against max.
+ *
+ * Returns the number of pages, and thus QDIO buffer elements, needed to cover
+ * skb data, including linear part and fragments, but excluding TCP header.
+ * (Exclusion of TCP header distinguishes it from qeth_get_elements_no().)
+ * Checks if the result plus extra_elems fits under the limit for the card.
+ * Returns 0 if it does not.
+ * Note: extra_elems is not included in the returned result.
+ */
+static int qeth_get_elements_no_tso(struct qeth_card *card,
+                        struct sk_buff *skb, int extra_elems)
 {
-        unsigned long tcpd = (unsigned long)tcp_hdr(skb) +
-                tcp_hdr(skb)->doff * 4;
-        int tcpd_len = skb_headlen(skb) - (tcpd - (unsigned long)skb->data);
-        int elements = PFN_UP(tcpd + tcpd_len - 1) - PFN_DOWN(tcpd);
-
-        elements += qeth_get_elements_for_frags(skb);
+        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);
 
+        if ((elements + extra_elems) > QETH_MAX_BUFFER_ELEMENTS(card)) {
+                QETH_DBF_MESSAGE(2,
+        "Invalid size of TSO IP packet (Number=%d / Length=%d). Discarded.\n",
+                                elements + extra_elems, skb->len);
+                return 0;
+        }
         return elements;
 }
 
@@ -2810,8 +2829,8 @@ static int qeth_l3_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
         int rc;
         u16 *tag;
         struct qeth_hdr *hdr = NULL;
-        int elements_needed = 0;
-        int elems;
+        int hdr_elements = 0;
+        int elements;
         struct qeth_card *card = dev->ml_priv;
         struct sk_buff *new_skb = NULL;
         int ipv = qeth_get_ip_version(skb);
@@ -2859,7 +2878,7 @@ static int qeth_l3_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
                 hdr = kmem_cache_alloc(qeth_core_header_cache, GFP_ATOMIC);
                 if (!hdr)
                         goto tx_drop;
-                elements_needed++;
+                hdr_elements++;
         } else {
                 /* create a clone with writeable headroom */
                 new_skb = skb_realloc_headroom(skb, sizeof(struct qeth_hdr_tso)
@@ -2895,7 +2914,7 @@ static int qeth_l3_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
          * chaining we can not send long frag lists
          */
         if (large_send) {
-                if (qeth_l3_tso_elements(new_skb) + 1 > 16) {
+                if (!qeth_get_elements_no_tso(card, new_skb, 1)) {
                         if (skb_linearize(new_skb))
                                 goto tx_drop;
                         if (card->options.performance_stats)
@@ -2909,7 +2928,7 @@ static int qeth_l3_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
                 memset(hdr, 0, sizeof(struct qeth_hdr_tso));
                 qeth_l3_fill_header(card, hdr, new_skb, ipv, cast_type);
                 qeth_tso_fill_header(card, hdr, new_skb);
-                elements_needed++;
+                hdr_elements++;
         } else {
                 if (data_offset < 0) {
                         hdr = (struct qeth_hdr *)skb_push(new_skb,
@@ -2930,31 +2949,29 @@ static int qeth_l3_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
                         qeth_l3_hdr_csum(card, hdr, new_skb);
         }
 
-        elems = qeth_get_elements_no(card, new_skb, elements_needed);
-        if (!elems) {
+        elements = qeth_get_elements_no(card, new_skb, hdr_elements);
+        if (!elements) {
                 if (data_offset >= 0)
                         kmem_cache_free(qeth_core_header_cache, hdr);
                 goto tx_drop;
         }
-        elements_needed += elems;
-        nr_frags = skb_shinfo(new_skb)->nr_frags;
+        elements += hdr_elements;
 
         if (card->info.type != QETH_CARD_TYPE_IQD) {
                 int len;
                 if (large_send)
                         len = ((unsigned long)tcp_hdr(new_skb) +
-                                tcp_hdr(new_skb)->doff * 4) -
+                                tcp_hdrlen(new_skb)) -
                                 (unsigned long)new_skb->data;
                 else
                         len = sizeof(struct qeth_hdr_layer3);
 
                 if (qeth_hdr_chk_and_bounce(new_skb, &hdr, len))
                         goto tx_drop;
-                rc = qeth_do_send_packet(card, queue, new_skb, hdr,
-                                         elements_needed);
+                rc = qeth_do_send_packet(card, queue, new_skb, hdr, elements);
         } else
                 rc = qeth_do_send_packet_fast(card, queue, new_skb, hdr,
-                                        elements_needed, data_offset, 0);
+                                        elements, data_offset, 0);
 
         if (!rc) {
                 card->stats.tx_packets++;
@@ -2962,6 +2979,7 @@ static int qeth_l3_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
                 if (new_skb != skb)
                         dev_kfree_skb_any(skb);
                 if (card->options.performance_stats) {
+                        nr_frags = skb_shinfo(new_skb)->nr_frags;
                         if (large_send) {
                                 card->perf_stats.large_send_bytes += tx_bytes;
                                 card->perf_stats.large_send_cnt++;