git: 71f8702f49a7 - main - mbuf: provide mc_get() that allocates struct mchain of given length
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Date: Mon, 08 Apr 2024 20:29:46 UTC
The branch main has been updated by glebius: URL: https://cgit.FreeBSD.org/src/commit/?id=71f8702f49a7c3294429e227a2b07cc3a0c408c7 commit 71f8702f49a7c3294429e227a2b07cc3a0c408c7 Author: Gleb Smirnoff <glebius@FreeBSD.org> AuthorDate: 2024-04-08 20:16:51 +0000 Commit: Gleb Smirnoff <glebius@FreeBSD.org> CommitDate: 2024-04-08 20:16:51 +0000 mbuf: provide mc_get() that allocates struct mchain of given length 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 --- sys/kern/kern_mbuf.c | 89 ++++++++++++++++++++++++++++++++-------------------- sys/sys/mbuf.h | 1 + 2 files changed, 56 insertions(+), 34 deletions(-) diff --git a/sys/kern/kern_mbuf.c b/sys/kern/kern_mbuf.c index 60c638735ec4..0df807e47bd6 100644 --- a/sys/kern/kern_mbuf.c +++ b/sys/kern/kern_mbuf.c @@ -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); } diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h index a5af2291123b..76c0005ae963 100644 --- a/sys/sys/mbuf.h +++ b/sys/sys/mbuf.h @@ -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_