aoe: use packets that work with the smallest-MTU local interface

Users with several network interfaces dedicated to AoE generally do not
configure them to support different-sized AoE data payloads on purpose.

For a given AoE target, there will be a set of local network interfaces
that can reach it.  Using only the payload that will fit in the
smallest-sized MTU of all those local interfaces greatly simplifies the
driver, especially in failure scenarios.

Signed-off-by: Ed Cashin <ecashin@coraid.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 87 insertions, 71 deletions

diff --git a/drivers/block/aoe/aoe.h b/drivers/block/aoe/aoe.h
index d0087de1780e..ffded64dcbeb 100644
--- a/drivers/block/aoe/aoe.h
+++ b/drivers/block/aoe/aoe.h
@@ -125,9 +125,8 @@ struct frame {
 
 struct aoeif {
         struct net_device *nd;
-        unsigned char lost;
-        unsigned char lostjumbo;
-        ushort maxbcnt;
+        ulong lost;
+        int bcnt;
 };
 
 struct aoetgt {
@@ -144,6 +143,7 @@ struct aoetgt {
         u16 useme;
         ulong falloc;
         ulong lastwadj;         /* last window adjustment */
+        int minbcnt;
         int wpkts, rpkts;
 };
 
@@ -172,6 +172,7 @@ struct aoedev {
                 struct bio *nxbio;
                 struct request *rq;
         } ip;
+        ulong maxbcnt;
         struct aoetgt *targets[NTARGETS];
         struct aoetgt **tgt;    /* target in use when working */
         struct aoetgt *htgt;    /* target needing rexmit assistance */
diff --git a/drivers/block/aoe/aoecmd.c b/drivers/block/aoe/aoecmd.c
index a1c5e8aa08c0..bbab40c8d67c 100644
--- a/drivers/block/aoe/aoecmd.c
+++ b/drivers/block/aoe/aoecmd.c
@@ -119,16 +119,18 @@ put_lba(struct aoe_atahdr *ah, sector_t lba)
         ah->lba5 = lba >>= 8;
 }
 
-static void
+static struct aoeif *
 ifrotate(struct aoetgt *t)
 {
-        t->ifp++;
-        if (t->ifp >= &t->ifs[NAOEIFS] || t->ifp->nd == NULL)
-                t->ifp = t->ifs;
-        if (t->ifp->nd == NULL) {
-                printk(KERN_INFO "aoe: no interface to rotate to\n");
-                BUG();
-        }
+        struct aoeif *ifp;
+
+        ifp = t->ifp;
+        ifp++;
+        if (ifp >= &t->ifs[NAOEIFS] || ifp->nd == NULL)
+                ifp = t->ifs;
+        if (ifp->nd == NULL)
+                return NULL;
+        return t->ifp = ifp;
 }
 
 static void
@@ -232,8 +234,8 @@ newframe(struct aoedev *d)
                 && t->ifp->nd) {
                         f = newtframe(d, t);
                         if (f) {
-                                d->tgt = tt;
                                 ifrotate(t);
+                                d->tgt = tt;
                                 return f;
                         }
                 }
@@ -300,7 +302,7 @@ aoecmd_ata_rw(struct aoedev *d)
                 return 0;
         t = *d->tgt;
         bv = buf->bv;
-        bcnt = t->ifp->maxbcnt;
+        bcnt = d->maxbcnt;
         if (bcnt == 0)
                 bcnt = DEFAULTBCNT;
         if (bcnt > buf->resid)
@@ -431,9 +433,14 @@ resend(struct aoedev *d, struct frame *f)
         u32 n;
 
         t = f->t;
-        ifrotate(t);
         n = newtag(t);
         skb = f->skb;
+        if (ifrotate(t) == NULL) {
+                /* probably can't happen, but set it up to fail anyway */
+                pr_info("aoe: resend: no interfaces to rotate to.\n");
+                ktcomplete(f, NULL);
+                return;
+        }
         h = (struct aoe_hdr *) skb_mac_header(skb);
         ah = (struct aoe_atahdr *) (h+1);
 
@@ -483,21 +490,6 @@ getif(struct aoetgt *t, struct net_device *nd)
         return NULL;
 }
 
-static struct aoeif *
-addif(struct aoetgt *t, struct net_device *nd)
-{
-        struct aoeif *p;
-
-        p = getif(t, NULL);
-        if (!p)
-                return NULL;
-        p->nd = nd;
-        p->maxbcnt = DEFAULTBCNT;
-        p->lost = 0;
-        p->lostjumbo = 0;
-        return p;
-}
-
 static void
 ejectif(struct aoetgt *t, struct aoeif *ifp)
 {
@@ -546,7 +538,11 @@ sthtith(struct aoedev *d)
                         resend(d, nf);
                 }
         }
-        /* he's clean, he's useless.  take away his interfaces */
+        /* We've cleaned up the outstanding so take away his
+         * interfaces so he won't be used.  We should remove him from
+         * the target array here, but cleaning up a target is
+         * involved.  PUNT!
+         */
         memset(ht->ifs, 0, sizeof ht->ifs);
         d->htgt = NULL;
         return 1;
@@ -1015,11 +1011,8 @@ noskb:	if (buf)
         case ATA_CMD_PIO_WRITE_EXT:
                 spin_lock_irq(&d->lock);
                 ifp = getif(t, skb->dev);
-                if (ifp) {
+                if (ifp)
                         ifp->lost = 0;
-                        if (n > DEFAULTBCNT)
-                                ifp->lostjumbo = 0;
-                }
                 if (d->htgt == t) /* I'll help myself, thank you. */
                         d->htgt = NULL;
                 spin_unlock_irq(&d->lock);
@@ -1292,6 +1285,56 @@ addtgt(struct aoedev *d, char *addr, ulong nframes)
         return *tt = t;
 }
 
+static void
+setdbcnt(struct aoedev *d)
+{
+        struct aoetgt **t, **e;
+        int bcnt = 0;
+
+        t = d->targets;
+        e = t + NTARGETS;
+        for (; t < e && *t; t++)
+                if (bcnt == 0 || bcnt > (*t)->minbcnt)
+                        bcnt = (*t)->minbcnt;
+        if (bcnt != d->maxbcnt) {
+                d->maxbcnt = bcnt;
+                pr_info("aoe: e%ld.%d: setting %d byte data frames\n",
+                        d->aoemajor, d->aoeminor, bcnt);
+        }
+}
+
+static void
+setifbcnt(struct aoetgt *t, struct net_device *nd, int bcnt)
+{
+        struct aoedev *d;
+        struct aoeif *p, *e;
+        int minbcnt;
+
+        d = t->d;
+        minbcnt = bcnt;
+        p = t->ifs;
+        e = p + NAOEIFS;
+        for (; p < e; p++) {
+                if (p->nd == NULL)
+                        break;          /* end of the valid interfaces */
+                if (p->nd == nd) {
+                        p->bcnt = bcnt; /* we're updating */
+                        nd = NULL;
+                } else if (minbcnt > p->bcnt)
+                        minbcnt = p->bcnt; /* find the min interface */
+        }
+        if (nd) {
+                if (p == e) {
+                        pr_err("aoe: device setifbcnt failure; too many interfaces.\n");
+                        return;
+                }
+                p->nd = nd;
+                p->bcnt = bcnt;
+        }
+        t->minbcnt = minbcnt;
+        setdbcnt(d);
+}
+
 void
 aoecmd_cfg_rsp(struct sk_buff *skb)
 {
@@ -1299,7 +1342,6 @@ aoecmd_cfg_rsp(struct sk_buff *skb)
         struct aoe_hdr *h;
         struct aoe_cfghdr *ch;
         struct aoetgt *t;
-        struct aoeif *ifp;
         ulong flags, sysminor, aoemajor;
         struct sk_buff *sl;
         struct sk_buff_head queue;
@@ -1345,32 +1387,13 @@ aoecmd_cfg_rsp(struct sk_buff *skb)
                 if (!t)
                         goto bail;
         }
-        ifp = getif(t, skb->dev);
-        if (!ifp) {
-                ifp = addif(t, skb->dev);
-                if (!ifp) {
-                        printk(KERN_INFO
-                                "aoe: device addif failure; "
-                                "too many interfaces?\n");
-                        goto bail;
-                }
-        }
-        if (ifp->maxbcnt) {
-                n = ifp->nd->mtu;
-                n -= sizeof (struct aoe_hdr) + sizeof (struct aoe_atahdr);
-                n /= 512;
-                if (n > ch->scnt)
-                        n = ch->scnt;
-                n = n ? n * 512 : DEFAULTBCNT;
-                if (n != ifp->maxbcnt) {
-                        printk(KERN_INFO
-                                "aoe: e%ld.%d: setting %d%s%s:%pm\n",
-                                d->aoemajor, d->aoeminor, n,
-                                " byte data frames on ", ifp->nd->name,
-                                t->addr);
-                        ifp->maxbcnt = n;
-                }
-        }
+        n = skb->dev->mtu;
+        n -= sizeof(struct aoe_hdr) + sizeof(struct aoe_atahdr);
+        n /= 512;
+        if (n > ch->scnt)
+                n = ch->scnt;
+        n = n ? n * 512 : DEFAULTBCNT;
+        setifbcnt(t, skb->dev, n);
 
         /* don't change users' perspective */
         if (d->nopen == 0) {
@@ -1391,22 +1414,14 @@ void
 aoecmd_cleanslate(struct aoedev *d)
 {
         struct aoetgt **t, **te;
-        struct aoeif *p, *e;
 
         d->mintimer = MINTIMER;
+        d->maxbcnt = 0;
 
         t = d->targets;
         te = t + NTARGETS;
-        for (; t < te && *t; t++) {
+        for (; t < te && *t; t++)
                 (*t)->maxout = (*t)->nframes;
-                p = (*t)->ifs;
-                e = p + NAOEIFS;
-                for (; p < e; p++) {
-                        p->lostjumbo = 0;
-                        p->lost = 0;
-                        p->maxbcnt = DEFAULTBCNT;
-                }
-        }
 }
 
 void