Re: ip_evictor can loop

["David S. Miller" <davem@xxxxxxxxxx>]

BTW, I forgot to mention to Parsanna when I discussed this
with him in private that ipv6 has an identical problem since
the ipv6 code is derived from the ipv4 stuff.

Fix for that one follows.

# This is a BitKeeper generated diff -Nru style patch.
#
# ChangeSet
#   2004/08/18 14:34:14-07:00 davem@xxxxxxxxxxxxxxxxxx 
#   [IPV6]: ip6_evictor() has same problem as ip_evictor().
#   
#   Signed-off-by: David S. Miller <davem@xxxxxxxxxx>
# 
# net/ipv6/reassembly.c
#   2004/08/18 14:33:54-07:00 davem@xxxxxxxxxxxxxxxxxx +22 -15
#   [IPV6]: ip6_evictor() has same problem as ip_evictor().
# 
diff -Nru a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
--- a/net/ipv6/reassembly.c     2004-08-18 19:13:13 -07:00
+++ b/net/ipv6/reassembly.c     2004-08-18 19:13:13 -07:00
@@ -195,14 +195,18 @@
 atomic_t ip6_frag_mem = ATOMIC_INIT(0);
 
 /* Memory Tracking Functions. */
-static inline void frag_kfree_skb(struct sk_buff *skb)
+static inline void frag_kfree_skb(struct sk_buff *skb, int *work)
 {
+       if (work)
+               *work -= skb->truesize;
        atomic_sub(skb->truesize, &ip6_frag_mem);
        kfree_skb(skb);
 }
 
-static inline void frag_free_queue(struct frag_queue *fq)
+static inline void frag_free_queue(struct frag_queue *fq, int *work)
 {
+       if (work)
+               *work -= sizeof(struct frag_queue);
        atomic_sub(sizeof(struct frag_queue), &ip6_frag_mem);
        kfree(fq);
 }
@@ -220,7 +224,7 @@
 /* Destruction primitives. */
 
 /* Complete destruction of fq. */
-static void ip6_frag_destroy(struct frag_queue *fq)
+static void ip6_frag_destroy(struct frag_queue *fq, int *work)
 {
        struct sk_buff *fp;
 
@@ -232,17 +236,17 @@
        while (fp) {
                struct sk_buff *xp = fp->next;
 
-               frag_kfree_skb(fp);
+               frag_kfree_skb(fp, work);
                fp = xp;
        }
 
-       frag_free_queue(fq);
+       frag_free_queue(fq, work);
 }
 
-static __inline__ void fq_put(struct frag_queue *fq)
+static __inline__ void fq_put(struct frag_queue *fq, int *work)
 {
        if (atomic_dec_and_test(&fq->refcnt))
-               ip6_frag_destroy(fq);
+               ip6_frag_destroy(fq, work);
 }
 
 /* Kill fq entry. It is not destroyed immediately,
@@ -264,10 +268,13 @@
 {
        struct frag_queue *fq;
        struct list_head *tmp;
+       int work;
 
-       for(;;) {
-               if (atomic_read(&ip6_frag_mem) <= sysctl_ip6frag_low_thresh)
-                       return;
+       work = atomic_read(&ip6_frag_mem) - sysctl_ip6frag_low_thresh;
+       if (work <= 0)
+               return;
+
+       while(work > 0) {
                read_lock(&ip6_frag_lock);
                if (list_empty(&ip6_frag_lru_list)) {
                        read_unlock(&ip6_frag_lock);
@@ -283,7 +290,7 @@
                        fq_kill(fq);
                spin_unlock(&fq->lock);
 
-               fq_put(fq);
+               fq_put(fq, &work);
                IP6_INC_STATS_BH(IPSTATS_MIB_REASMFAILS);
        }
 }
@@ -320,7 +327,7 @@
        }
 out:
        spin_unlock(&fq->lock);
-       fq_put(fq);
+       fq_put(fq, NULL);
 }
 
 /* Creation primitives. */
@@ -340,7 +347,7 @@
                        atomic_inc(&fq->refcnt);
                        write_unlock(&ip6_frag_lock);
                        fq_in->last_in |= COMPLETE;
-                       fq_put(fq_in);
+                       fq_put(fq_in, NULL);
                        return fq;
                }
        }
@@ -539,7 +546,7 @@
                                fq->fragments = next;
 
                        fq->meat -= free_it->len;
-                       frag_kfree_skb(free_it);
+                       frag_kfree_skb(free_it, NULL);
                }
        }
 
@@ -734,7 +741,7 @@
                        ret = ip6_frag_reasm(fq, skbp, nhoffp, dev);
 
                spin_unlock(&fq->lock);
-               fq_put(fq);
+               fq_put(fq, NULL);
                return ret;
        }