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aoe: zero copy write 1 of 2
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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>
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Ed L. Cashin authored and Greg Kroah-Hartman committed Oct 18, 2006
1 parent 2fdc0ea commit e407a7f
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Showing 3 changed files with 69 additions and 74 deletions.
7 changes: 2 additions & 5 deletions drivers/block/aoe/aoe.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand Down Expand Up @@ -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);
Expand Down
94 changes: 37 additions & 57 deletions drivers/block/aoe/aoecmd.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand All @@ -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)
{
Expand Down Expand Up @@ -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;
Expand All @@ -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;
Expand All @@ -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,
Expand All @@ -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;
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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)
Expand Down Expand Up @@ -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;
Expand Down
42 changes: 30 additions & 12 deletions drivers/block/aoe/aoedev.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -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);
Expand Down

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