cxgb3 - fix interaction with pktgen

Do not use skb->cb to stash unmap info,
save the info to the descriptor state.

Signed-off-by: Divy Le Ray <divy@chelsio.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 40 insertions, 42 deletions

diff --git a/drivers/net/cxgb3/sge.c b/drivers/net/cxgb3/sge.c
index c15e43a8543b..7b13d8a31e38 100644
--- a/drivers/net/cxgb3/sge.c
+++ b/drivers/net/cxgb3/sge.c
@@ -91,6 +91,10 @@ struct rx_desc {
 
 struct tx_sw_desc {             /* SW state per Tx descriptor */
         struct sk_buff *skb;
+        u8 eop;       /* set if last descriptor for packet */
+        u8 addr_idx;  /* buffer index of first SGL entry in descriptor */
+        u8 fragidx;   /* first page fragment associated with descriptor */
+        s8 sflit;     /* start flit of first SGL entry in descriptor */
 };
 
 struct rx_sw_desc {                /* SW state per Rx descriptor */
@@ -109,13 +113,6 @@ struct rsp_desc {		/* response queue descriptor */
         u8 intr_gen;
 };
 
-struct unmap_info {             /* packet unmapping info, overlays skb->cb */
-        int sflit;              /* start flit of first SGL entry in Tx descriptor */
-        u16 fragidx;            /* first page fragment in current Tx descriptor */
-        u16 addr_idx;           /* buffer index of first SGL entry in descriptor */
-        u32 len;                /* mapped length of skb main body */
-};
-
 /*
  * Holds unmapping information for Tx packets that need deferred unmapping.
  * This structure lives at skb->head and must be allocated by callers.
@@ -209,32 +206,36 @@ static inline int need_skb_unmap(void)
  *
  *      Unmap the main body of an sk_buff and its page fragments, if any.
  *      Because of the fairly complicated structure of our SGLs and the desire
- *      to conserve space for metadata, we keep the information necessary to
- *      unmap an sk_buff partly in the sk_buff itself (in its cb), and partly
- *      in the Tx descriptors (the physical addresses of the various data
- *      buffers).  The send functions initialize the state in skb->cb so we
- *      can unmap the buffers held in the first Tx descriptor here, and we
- *      have enough information at this point to update the state for the next
- *      Tx descriptor.
+ *      to conserve space for metadata, the information necessary to unmap an
+ *      sk_buff is spread across the sk_buff itself (buffer lengths), the HW Tx
+ *      descriptors (the physical addresses of the various data buffers), and
+ *      the SW descriptor state (assorted indices).  The send functions
+ *      initialize the indices for the first packet descriptor so we can unmap
+ *      the buffers held in the first Tx descriptor here, and we have enough
+ *      information at this point to set the state for the next Tx descriptor.
+ *
+ *      Note that it is possible to clean up the first descriptor of a packet
+ *      before the send routines have written the next descriptors, but this
+ *      race does not cause any problem.  We just end up writing the unmapping
+ *      info for the descriptor first.
  */
 static inline void unmap_skb(struct sk_buff *skb, struct sge_txq *q,
                              unsigned int cidx, struct pci_dev *pdev)
 {
         const struct sg_ent *sgp;
-        struct unmap_info *ui = (struct unmap_info *)skb->cb;
-        int nfrags, frag_idx, curflit, j = ui->addr_idx;
+        struct tx_sw_desc *d = &q->sdesc[cidx];
+        int nfrags, frag_idx, curflit, j = d->addr_idx;
 
-        sgp = (struct sg_ent *)&q->desc[cidx].flit[ui->sflit];
+        sgp = (struct sg_ent *)&q->desc[cidx].flit[d->sflit];
+        frag_idx = d->fragidx;
 
-        if (ui->len) {
-                pci_unmap_single(pdev, be64_to_cpu(sgp->addr[0]), ui->len,
-                                 PCI_DMA_TODEVICE);
-                ui->len = 0;    /* so we know for next descriptor for this skb */
+        if (frag_idx == 0 && skb_headlen(skb)) {
+                pci_unmap_single(pdev, be64_to_cpu(sgp->addr[0]),
+                                 skb_headlen(skb), PCI_DMA_TODEVICE);
                 j = 1;
         }
 
-        frag_idx = ui->fragidx;
-        curflit = ui->sflit + 1 + j;
+        curflit = d->sflit + 1 + j;
         nfrags = skb_shinfo(skb)->nr_frags;
 
         while (frag_idx < nfrags && curflit < WR_FLITS) {
@@ -250,10 +251,11 @@ static inline void unmap_skb(struct sk_buff *skb, struct sge_txq *q,
                 frag_idx++;
         }
 
-        if (frag_idx < nfrags) {        /* SGL continues into next Tx descriptor */
-                ui->fragidx = frag_idx;
-                ui->addr_idx = j;
-                ui->sflit = curflit - WR_FLITS - j;     /* sflit can be -1 */
+        if (frag_idx < nfrags) {   /* SGL continues into next Tx descriptor */
+                d = cidx + 1 == q->size ? q->sdesc : d + 1;
+                d->fragidx = frag_idx;
+                d->addr_idx = j;
+                d->sflit = curflit - WR_FLITS - j; /* sflit can be -1 */
         }
 }
 
@@ -281,7 +283,7 @@ static void free_tx_desc(struct adapter *adapter, struct sge_txq *q,
                 if (d->skb) {   /* an SGL is present */
                         if (need_unmap)
                                 unmap_skb(d->skb, q, cidx, pdev);
-                        if (d->skb->priority == cidx)
+                        if (d->eop)
                                 kfree_skb(d->skb);
                 }
                 ++d;
@@ -912,15 +914,13 @@ static void write_wr_hdr_sgl(unsigned int ndesc, struct sk_buff *skb,
 
         sd->skb = skb;
         if (need_skb_unmap()) {
-                struct unmap_info *ui = (struct unmap_info *)skb->cb;
-
-                ui->fragidx = 0;
-                ui->addr_idx = 0;
-                ui->sflit = flits;
+                sd->fragidx = 0;
+                sd->addr_idx = 0;
+                sd->sflit = flits;
         }
 
         if (likely(ndesc == 1)) {
-                skb->priority = pidx;
+                sd->eop = 1;
                 wrp->wr_hi = htonl(F_WR_SOP | F_WR_EOP | V_WR_DATATYPE(1) |
                                    V_WR_SGLSFLT(flits)) | wr_hi;
                 wmb();
@@ -948,6 +948,7 @@ static void write_wr_hdr_sgl(unsigned int ndesc, struct sk_buff *skb,
 
                         fp += avail;
                         d++;
+                        sd->eop = 0;
                         sd++;
                         if (++pidx == q->size) {
                                 pidx = 0;
@@ -966,7 +967,7 @@ static void write_wr_hdr_sgl(unsigned int ndesc, struct sk_buff *skb,
                         wr_gen2(d, gen);
                         flits = 1;
                 }
-                skb->priority = pidx;
+                sd->eop = 1;
                 wrp->wr_hi |= htonl(F_WR_EOP);
                 wmb();
                 wp->wr_lo = htonl(V_WR_LEN(WR_FLITS) | V_WR_GEN(ogen)) | wr_lo;
@@ -1051,8 +1052,6 @@ static void write_tx_pkt_wr(struct adapter *adap, struct sk_buff *skb,
 
         sgp = ndesc == 1 ? (struct sg_ent *)&d->flit[flits] : sgl;
         sgl_flits = make_sgl(skb, sgp, skb->data, skb_headlen(skb), adap->pdev);
-        if (need_skb_unmap())
-                ((struct unmap_info *)skb->cb)->len = skb_headlen(skb);
 
         write_wr_hdr_sgl(ndesc, skb, d, pidx, q, sgl, flits, sgl_flits, gen,
                          htonl(V_WR_OP(FW_WROPCODE_TUNNEL_TX_PKT) | compl),
@@ -1380,13 +1379,14 @@ static void deferred_unmap_destructor(struct sk_buff *skb)
         const dma_addr_t *p;
         const struct skb_shared_info *si;
         const struct deferred_unmap_info *dui;
-        const struct unmap_info *ui = (struct unmap_info *)skb->cb;
 
         dui = (struct deferred_unmap_info *)skb->head;
         p = dui->addr;
 
-        if (ui->len)
-                pci_unmap_single(dui->pdev, *p++, ui->len, PCI_DMA_TODEVICE);
+        if (skb->tail - skb->transport_header)
+                pci_unmap_single(dui->pdev, *p++,
+                                 skb->tail - skb->transport_header,
+                                 PCI_DMA_TODEVICE);
 
         si = skb_shinfo(skb);
         for (i = 0; i < si->nr_frags; i++)
@@ -1451,8 +1451,6 @@ static void write_ofld_wr(struct adapter *adap, struct sk_buff *skb,
         if (need_skb_unmap()) {
                 setup_deferred_unmapping(skb, adap->pdev, sgp, sgl_flits);
                 skb->destructor = deferred_unmap_destructor;
-                ((struct unmap_info *)skb->cb)->len = (skb->tail -
-                                                       skb->transport_header);
         }
 
         write_wr_hdr_sgl(ndesc, skb, d, pidx, q, sgl, flits, sgl_flits,