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/aoe.h b/drivers/block/aoe/aoe.h
index 507c377..fa2d804 100644 (file)
--- a/drivers/block/aoe/aoe.h
+++ b/drivers/block/aoe/aoe.h
@@ -107,11 +107,7 @@ struct frame {
        ulong waited;
        struct buf *buf;
        char *bufaddr;
-       int writedatalen;
-       int ndata;
-
-       /* largest possible */
-       unsigned char data[sizeof(struct aoe_hdr) + sizeof(struct aoe_atahdr)];
+       struct sk_buff *skb;
 };
 
 struct aoedev {
@@ -157,6 +153,7 @@ void aoecmd_cfg(ushort aoemajor, unsigned char aoeminor);
 void aoecmd_ata_rsp(struct sk_buff *);
 void aoecmd_cfg_rsp(struct sk_buff *);
 void aoecmd_sleepwork(void *vp);
+struct sk_buff *new_skb(ulong);
 
 int aoedev_init(void);
 void aoedev_exit(void);

diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index d1d8759..1aeb296 100644 (file)
--- 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 @@ new_skb(struct net_device *if_dev, ulong len)
        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 @@ aoecmd_ata_rw(struct aoedev *d, struct frame *f)
                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 @@ aoecmd_ata_rw(struct aoedev *d, struct frame *f)
        }
 
        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 @@ aoecmd_ata_rw(struct aoedev *d, struct frame *f)
                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 @@ aoecmd_cfg_pkts(ushort aoemajor, unsigned char aoeminor, struct sk_buff **tail)
                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 @@ rexmit(struct aoedev *d, struct frame *f)
                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 @@ aoecmd_ata_rsp(struct sk_buff *skb)
        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 @@ aoecmd_ata_id(struct aoedev *d)
        }
 
        /* 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;

diff --git a/drivers/block/aoe/aoedev.c b/drivers/block/aoe/aoedev.c
index c7e05ed..abf1d3c 100644 (file)
--- a/drivers/block/aoe/aoedev.c
+++ b/drivers/block/aoe/aoedev.c
@@ -63,22 +63,32 @@ aoedev_newdev(ulong nframes)
        struct frame *f, *e;
 
        d = kzalloc(sizeof *d, GFP_ATOMIC);
-       if (d == NULL)
-               return NULL;
        f = kcalloc(nframes, sizeof *f, GFP_ATOMIC);
-       if (f == NULL) {
-               kfree(d);
+       switch (!d || !f) {
+       case 0:
+               d->nframes = nframes;
+               d->frames = f;
+               e = f + nframes;
+               for (; f<e; f++) {
+                       f->tag = FREETAG;
+                       f->skb = new_skb(ETH_ZLEN);
+                       if (!f->skb)
+                               break;
+               }
+               if (f == e)
+                       break;
+               while (f > d->frames) {
+                       f--;
+                       dev_kfree_skb(f->skb);
+               }
+       default:
+               if (f)
+                       kfree(f);
+               if (d)
+                       kfree(d);
                return NULL;
        }
-
        INIT_WORK(&d->work, aoecmd_sleepwork, d);
-
-       d->nframes = nframes;
-       d->frames = f;
-       e = f + nframes;
-       for (; f<e; f++)
-               f->tag = FREETAG;
-
        spin_lock_init(&d->lock);
        init_timer(&d->timer);
        d->timer.data = (ulong) d;
@@ -160,11 +170,19 @@ aoedev_by_sysminor_m(ulong sysminor, ulong bufcnt)
 static void
 aoedev_freedev(struct aoedev *d)
 {
+       struct frame *f, *e;
+
        if (d->gd) {
                aoedisk_rm_sysfs(d);
                del_gendisk(d->gd);
                put_disk(d->gd);
        }
+       f = d->frames;
+       e = f + d->nframes;
+       for (; f<e; f++) {
+               skb_shinfo(f->skb)->nr_frags = 0;
+               dev_kfree_skb(f->skb);
+       }
        kfree(d->frames);
        if (d->bufpool)
                mempool_destroy(d->bufpool);