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mbuf: provide mc_get() that allocates struct mchain of given length

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Implement m_getm2(), which is widely used via m_getm() macro, as a wrapper
around mc_get().  New code is advised to use mc_get().

Reviewed by:		markj, tuexen
Differential Revision:	https://reviews.freebsd.org/D44149
This commit is contained in:
Gleb Smirnoff 2024-04-08 13:16:51 -07:00
parent fd01798fc4
commit 71f8702f49
2 changed files with 56 additions and 34 deletions
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89
sys/kern/kern_mbuf.c
View File

@ -1446,34 +1446,36 @@ m_getjcl(int how, short type, int flags, int size)
}
/*
* 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 @@ m_getm2(struct mbuf *m, int len, int how, short type, int flags)
* 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);
}

1
sys/sys/mbuf.h
View File

@ -1795,6 +1795,7 @@ mc_remove(struct mchain *mc, struct mbuf *m)
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_