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diff --git a/sys/kern/kern_mbuf.c b/sys/kern/kern_mbuf.c
--- a/sys/kern/kern_mbuf.c
+++ b/sys/kern/kern_mbuf.c
@@ -1446,34 +1446,36 @@
}
/*
- * Allocate a given length worth of mbufs and/or clusters (whatever fits
- * best) and return a pointer to the top of the allocated chain. If an
- * existing mbuf chain is provided, then we will append the new chain
- * to the existing one and return a pointer to the provided mbuf.
+ * Allocate mchain of a given length of mbufs and/or clusters (whatever fits
+ * best). May fail due to ENOMEM. In case of failure state of mchain is
+ * inconsistent.
*/
-struct mbuf *
-m_getm2(struct mbuf *m, int len, int how, short type, int flags)
+int
+mc_get(struct mchain *mc, u_int length, int how, short type, int flags)
{
- struct mbuf *mb, *nm = NULL, *mtail = NULL;
+ struct mbuf *mb;
+ u_int progress;
- KASSERT(len >= 0, ("%s: len is < 0", __func__));
+ MPASS(length >= 0);
- /* Validate flags. */
+ *mc = MCHAIN_INITIALIZER(mc);
flags &= (M_PKTHDR | M_EOR);
-
- /* Packet header mbuf must be first in chain. */
- if ((flags & M_PKTHDR) && m != NULL)
- flags &= ~M_PKTHDR;
+ progress = 0;
/* Loop and append maximum sized mbufs to the chain tail. */
- while (len > 0) {
- mb = NULL;
- if (len > MCLBYTES) {
+ do {
+ if (length - progress > MCLBYTES) {
+ /*
+ * M_NOWAIT here is intentional, it avoids blocking if
+ * the jumbop zone is exhausted. See 796d4eb89e2c and
+ * D26150 for more detail.
+ */
mb = m_getjcl(M_NOWAIT, type, (flags & M_PKTHDR),
MJUMPAGESIZE);
- }
+ } else
+ mb = NULL;
if (mb == NULL) {
- if (len >= MINCLSIZE)
+ if (length - progress >= MINCLSIZE)
mb = m_getcl(how, type, (flags & M_PKTHDR));
else if (flags & M_PKTHDR)
mb = m_gethdr(how, type);
@@ -1485,31 +1487,50 @@
* allocated.
*/
if (mb == NULL) {
- m_freem(nm);
- return (NULL);
+ m_freem(mc_first(mc));
+ return (ENOMEM);
}
}
- /* Book keeping. */
- len -= M_SIZE(mb);
- if (mtail != NULL)
- mtail->m_next = mb;
- else
- nm = mb;
- mtail = mb;
- flags &= ~M_PKTHDR; /* Only valid on the first mbuf. */
- }
+ progress += M_SIZE(mb);
+ mc_append(mc, mb);
+ /* Only valid on the first mbuf. */
+ flags &= ~M_PKTHDR;
+ } while (progress < length);
if (flags & M_EOR)
- mtail->m_flags |= M_EOR; /* Only valid on the last mbuf. */
+ /* Only valid on the last mbuf. */
+ mc_last(mc)->m_flags |= M_EOR;
+
+ return (0);
+}
+
+/*
+ * Allocate a given length worth of mbufs and/or clusters (whatever fits
+ * best) and return a pointer to the top of the allocated chain. If an
+ * existing mbuf chain is provided, then we will append the new chain
+ * to the existing one and return a pointer to the provided mbuf.
+ */
+struct mbuf *
+m_getm2(struct mbuf *m, int len, int how, short type, int flags)
+{
+ struct mchain mc;
+
+ /* Packet header mbuf must be first in chain. */
+ if (m != NULL && (flags & M_PKTHDR))
+ flags &= ~M_PKTHDR;
+
+ if (__predict_false(mc_get(&mc, len, how, type, flags) != 0))
+ return (NULL);
/* If mbuf was supplied, append new chain to the end of it. */
if (m != NULL) {
- for (mtail = m; mtail->m_next != NULL; mtail = mtail->m_next)
- ;
- mtail->m_next = nm;
+ struct mbuf *mtail;
+
+ mtail = m_last(m);
+ mtail->m_next = mc_first(&mc);
mtail->m_flags &= ~M_EOR;
} else
- m = nm;
+ m = mc_first(&mc);
return (m);
}
diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -1795,6 +1795,7 @@
mc_dec(mc, m);
}
+int mc_get(struct mchain *, u_int, int, short, int);
int mc_split(struct mchain *, struct mchain *, u_int, int);
#ifdef _SYS_TIMESPEC_H_

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