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Add m_ensure_contig() routine, which is equivalent to m_pullup, but does not

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destroy the mbuf chain on failure (it is kept valid).
This commit is contained in:
rmind 2013-01-19 00:51:52 +00:00
parent 6459287701
commit d3cb55ca37
2 changed files with 48 additions and 32 deletions
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76
sys/kern/uipc_mbuf.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: uipc_mbuf.c,v 1.147 2012/10/18 19:33:38 para Exp $ */
/* $NetBSD: uipc_mbuf.c,v 1.148 2013/01/19 00:51:52 rmind Exp $ */
/*-
* Copyright (c) 1999, 2001 The NetBSD Foundation, Inc.
@ -62,7 +62,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: uipc_mbuf.c,v 1.147 2012/10/18 19:33:38 para Exp $");
__KERNEL_RCSID(0, "$NetBSD: uipc_mbuf.c,v 1.148 2013/01/19 00:51:52 rmind Exp $");
#include "opt_mbuftrace.h"
#include "opt_nmbclusters.h"
@ -906,21 +906,18 @@ m_adj(struct mbuf *mp, int req_len)
}
/*
* Rearrange an mbuf chain so that len bytes are contiguous
* and in the data area of an mbuf (so that mtod and dtom
* will work for a structure of size len). Returns the resulting
* mbuf chain on success, frees it and returns null on failure.
* If there is room, it will add up to max_protohdr-len extra bytes to the
* contiguous region in an attempt to avoid being called next time.
* m_ensure_contig: rearrange an mbuf chain that given length of bytes
* would be contiguous and in the data area of an mbuf (therefore, mtod()
* would work for a structure of given length).
*
* => On success, returns true and the resulting mbuf chain; false otherwise.
* => The mbuf chain may change, but is always preserved valid.
*/
int MPFail;
struct mbuf *
m_pullup(struct mbuf *n, int len)
bool
m_ensure_contig(struct mbuf **m0, int len)
{
struct mbuf *m;
int count;
int space;
struct mbuf *n = *m0, *m;
size_t count, space;
/*
* If first mbuf has no cluster, and has room for len bytes
@ -929,17 +926,20 @@ m_pullup(struct mbuf *n, int len)
*/
if ((n->m_flags & M_EXT) == 0 &&
n->m_data + len < &n->m_dat[MLEN] && n->m_next) {
if (n->m_len >= len)
return (n);
if (n->m_len >= len) {
return true;
}
m = n;
n = n->m_next;
len -= m->m_len;
} else {
if (len > MHLEN)
goto bad;
if (len > MHLEN) {
return false;
}
MGET(m, M_DONTWAIT, n->m_type);
if (m == 0)
goto bad;
if (m == NULL) {
return false;
}
MCLAIM(m, n->m_owner);
m->m_len = 0;
if (n->m_flags & M_PKTHDR) {
@ -948,7 +948,7 @@ m_pullup(struct mbuf *n, int len)
}
space = &m->m_dat[MLEN] - (m->m_data + m->m_len);
do {
count = min(min(max(len, max_protohdr), space), n->m_len);
count = MIN(MIN(MAX(len, max_protohdr), space), n->m_len);
memcpy(mtod(m, char *) + m->m_len, mtod(n, void *),
(unsigned)count);
len -= count;
@ -960,16 +960,30 @@ m_pullup(struct mbuf *n, int len)
else
n = m_free(n);
} while (len > 0 && n);
if (len > 0) {
(void) m_free(m);
goto bad;
}
m->m_next = n;
return (m);
bad:
m_freem(n);
MPFail++;
return (NULL);
*m0 = m;
return len <= 0;
}
/*
* m_pullup: same as m_ensure_contig(), but destroys mbuf chain on error.
*/
int MPFail;
struct mbuf *
m_pullup(struct mbuf *n, int len)
{
struct mbuf *m = n;
if (!m_ensure_contig(&m, len)) {
KASSERT(m != NULL);
m_freem(m);
MPFail++;
m = NULL;
}
return m;
}
/*

4
sys/sys/mbuf.h
View File

@ -1,4 +1,4 @@
/* $NetBSD: mbuf.h,v 1.150 2012/12/27 14:41:10 christos Exp $ */
/* $NetBSD: mbuf.h,v 1.151 2013/01/19 00:51:52 rmind Exp $ */
/*-
* Copyright (c) 1996, 1997, 1999, 2001, 2007 The NetBSD Foundation, Inc.
@ -854,6 +854,8 @@ void m_ext_free(struct mbuf *);
char * m_mapin(struct mbuf *);
void m_move_pkthdr(struct mbuf *to, struct mbuf *from);
bool m_ensure_contig(struct mbuf **, int);
/* Inline routines. */
static __inline u_int m_length(const struct mbuf *) __unused;