aoe: zero copy write 1 of 2
Avoid memory copy on writes.
(This patch depends on fixes in patch 9 to follow.)
Although skb->len should not be set when working with linear skbuffs,
the skb->tail pointer maintained by skb_put/skb_trim is not relevant
to what happens when the skb_fill_page_desc function is called. This
issue was raised without comment in linux-kernel and netdev earlier
this month:
http://thread.gmane.org/gmane.linux.kernel/446474/
http://thread.gmane.org/gmane.linux.network/45444/
So until there is something analogous to skb_put that works for
zero-copy write skbuffs, we will do what the other callers of
skb_fill_page_desc are doing.
Signed-off-by: "Ed L. Cashin" <ecashin@coraid.com>
Acked-by: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index d1d8759..1aeb296 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -17,15 +17,14 @@
#define MAXTIMER (HZ << 1)
#define MAXWAIT (60 * 3) /* After MAXWAIT seconds, give up and fail dev */
-static struct sk_buff *
-new_skb(struct net_device *if_dev, ulong len)
+struct sk_buff *
+new_skb(ulong len)
{
struct sk_buff *skb;
skb = alloc_skb(len, GFP_ATOMIC);
if (skb) {
skb->nh.raw = skb->mac.raw = skb->data;
- skb->dev = if_dev;
skb->protocol = __constant_htons(ETH_P_AOE);
skb->priority = 0;
skb_put(skb, len);
@@ -40,29 +39,6 @@
return skb;
}
-static struct sk_buff *
-skb_prepare(struct aoedev *d, struct frame *f)
-{
- struct sk_buff *skb;
- char *p;
-
- skb = new_skb(d->ifp, f->ndata + f->writedatalen);
- if (!skb) {
- printk(KERN_INFO "aoe: skb_prepare: failure to allocate skb\n");
- return NULL;
- }
-
- p = skb->mac.raw;
- memcpy(p, f->data, f->ndata);
-
- if (f->writedatalen) {
- p += sizeof(struct aoe_hdr) + sizeof(struct aoe_atahdr);
- memcpy(p, f->bufaddr, f->writedatalen);
- }
-
- return skb;
-}
-
static struct frame *
getframe(struct aoedev *d, int tag)
{
@@ -129,10 +105,11 @@
bcnt = MAXATADATA;
/* initialize the headers & frame */
- h = (struct aoe_hdr *) f->data;
+ skb = f->skb;
+ h = (struct aoe_hdr *) skb->mac.raw;
ah = (struct aoe_atahdr *) (h+1);
- f->ndata = sizeof *h + sizeof *ah;
- memset(h, 0, f->ndata);
+ skb->len = sizeof *h + sizeof *ah;
+ memset(h, 0, skb->len);
f->tag = aoehdr_atainit(d, h);
f->waited = 0;
f->buf = buf;
@@ -155,11 +132,13 @@
}
if (bio_data_dir(buf->bio) == WRITE) {
+ skb_fill_page_desc(skb, 0, virt_to_page(f->bufaddr),
+ offset_in_page(f->bufaddr), bcnt);
ah->aflags |= AOEAFL_WRITE;
- f->writedatalen = bcnt;
} else {
+ skb_shinfo(skb)->nr_frags = 0;
+ skb->len = ETH_ZLEN;
writebit = 0;
- f->writedatalen = 0;
}
ah->cmdstat = WIN_READ | writebit | extbit;
@@ -179,15 +158,14 @@
buf->bufaddr = page_address(buf->bv->bv_page) + buf->bv->bv_offset;
}
- skb = skb_prepare(d, f);
- if (skb) {
- skb->next = NULL;
- if (d->sendq_hd)
- d->sendq_tl->next = skb;
- else
- d->sendq_hd = skb;
- d->sendq_tl = skb;
- }
+ skb->dev = d->ifp;
+ skb_get(skb);
+ skb->next = NULL;
+ if (d->sendq_hd)
+ d->sendq_tl->next = skb;
+ else
+ d->sendq_hd = skb;
+ d->sendq_tl = skb;
}
/* some callers cannot sleep, and they can call this function,
@@ -209,11 +187,12 @@
if (!is_aoe_netif(ifp))
continue;
- skb = new_skb(ifp, sizeof *h + sizeof *ch);
+ skb = new_skb(sizeof *h + sizeof *ch);
if (skb == NULL) {
printk(KERN_INFO "aoe: aoecmd_cfg: skb alloc failure\n");
continue;
}
+ skb->dev = ifp;
if (sl_tail == NULL)
sl_tail = skb;
h = (struct aoe_hdr *) skb->mac.raw;
@@ -283,21 +262,21 @@
d->aoemajor, d->aoeminor, f->tag, jiffies, n);
aoechr_error(buf);
- h = (struct aoe_hdr *) f->data;
+ skb = f->skb;
+ h = (struct aoe_hdr *) skb->mac.raw;
f->tag = n;
h->tag = cpu_to_be32(n);
memcpy(h->dst, d->addr, sizeof h->dst);
memcpy(h->src, d->ifp->dev_addr, sizeof h->src);
- skb = skb_prepare(d, f);
- if (skb) {
- skb->next = NULL;
- if (d->sendq_hd)
- d->sendq_tl->next = skb;
- else
- d->sendq_hd = skb;
- d->sendq_tl = skb;
- }
+ skb->dev = d->ifp;
+ skb_get(skb);
+ skb->next = NULL;
+ if (d->sendq_hd)
+ d->sendq_tl->next = skb;
+ else
+ d->sendq_hd = skb;
+ d->sendq_tl = skb;
}
static int
@@ -514,7 +493,7 @@
calc_rttavg(d, tsince(f->tag));
ahin = (struct aoe_atahdr *) (hin+1);
- ahout = (struct aoe_atahdr *) (f->data + sizeof(struct aoe_hdr));
+ ahout = (struct aoe_atahdr *) (f->skb->mac.raw + sizeof(struct aoe_hdr));
buf = f->buf;
if (ahout->cmdstat == WIN_IDENTIFY)
@@ -620,20 +599,21 @@
}
/* initialize the headers & frame */
- h = (struct aoe_hdr *) f->data;
+ skb = f->skb;
+ h = (struct aoe_hdr *) skb->mac.raw;
ah = (struct aoe_atahdr *) (h+1);
- f->ndata = sizeof *h + sizeof *ah;
- memset(h, 0, f->ndata);
+ skb->len = sizeof *h + sizeof *ah;
+ memset(h, 0, skb->len);
f->tag = aoehdr_atainit(d, h);
f->waited = 0;
- f->writedatalen = 0;
/* set up ata header */
ah->scnt = 1;
ah->cmdstat = WIN_IDENTIFY;
ah->lba3 = 0xa0;
- skb = skb_prepare(d, f);
+ skb->dev = d->ifp;
+ skb_get(skb);
d->rttavg = MAXTIMER;
d->timer.function = rexmit_timer;