FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_mbuf.c

     /*-
      * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
      *
      * Copyright (c) 2004, 2005,
      *      Bosko Milekic <bmilekic@FreeBSD.org>.  All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice unmodified, this list of conditions and the following
     *    disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_param.h"
    
    #include <sys/param.h>
    #include <sys/domainset.h>
    #include <sys/malloc.h>
    #include <sys/types.h>
    #include <sys/systm.h>
    #include <sys/mbuf.h>
    #include <sys/domain.h>
    #include <sys/eventhandler.h>
    #include <sys/kernel.h>
    #include <sys/limits.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/protosw.h>
    #include <sys/smp.h>
    #include <sys/sysctl.h>
    
    #include <vm/vm.h>
    #include <vm/vm_extern.h>
    #include <vm/vm_kern.h>
    #include <vm/vm_page.h>
    #include <vm/vm_map.h>
    #include <vm/uma.h>
    #include <vm/uma_dbg.h>
    
    /*
     * In FreeBSD, Mbufs and Mbuf Clusters are allocated from UMA
     * Zones.
     *
     * Mbuf Clusters (2K, contiguous) are allocated from the Cluster
     * Zone.  The Zone can be capped at kern.ipc.nmbclusters, if the
     * administrator so desires.
     *
     * Mbufs are allocated from a UMA Master Zone called the Mbuf
     * Zone.
     *
     * Additionally, FreeBSD provides a Packet Zone, which it
     * configures as a Secondary Zone to the Mbuf Master Zone,
     * thus sharing backend Slab kegs with the Mbuf Master Zone.
     *
     * Thus common-case allocations and locking are simplified:
     *
     *  m_clget()                m_getcl()
     *    |                         |
     *    |   .------------>[(Packet Cache)]    m_get(), m_gethdr()
     *    |   |             [     Packet   ]            |
     *  [(Cluster Cache)]   [    Secondary ]   [ (Mbuf Cache)     ]
     *  [ Cluster Zone  ]   [     Zone     ]   [ Mbuf Master Zone ]
     *        |                       \________         |
     *  [ Cluster Keg   ]                      \       /
     *        |                              [ Mbuf Keg   ]
     *  [ Cluster Slabs ]                         |
     *        |                              [ Mbuf Slabs ]
     *         \____________(VM)_________________/
     *
     *
     * Whenever an object is allocated with uma_zalloc() out of
     * one of the Zones its _ctor_ function is executed.  The same
     * for any deallocation through uma_zfree() the _dtor_ function
     * is executed.
     *
     * Caches are per-CPU and are filled from the Master Zone.
     *
     * Whenever an object is allocated from the underlying global
     * memory pool it gets pre-initialized with the _zinit_ functions.
     * When the Keg's are overfull objects get decommissioned with
    * _zfini_ functions and free'd back to the global memory pool.
    *
    */
   
   int nmbufs;                     /* limits number of mbufs */
   int nmbclusters;                /* limits number of mbuf clusters */
   int nmbjumbop;                  /* limits number of page size jumbo clusters */
   int nmbjumbo9;                  /* limits number of 9k jumbo clusters */
   int nmbjumbo16;                 /* limits number of 16k jumbo clusters */
   
   static quad_t maxmbufmem;       /* overall real memory limit for all mbufs */
   
   SYSCTL_QUAD(_kern_ipc, OID_AUTO, maxmbufmem, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &maxmbufmem, 0,
       "Maximum real memory allocatable to various mbuf types");
   
   /*
    * tunable_mbinit() has to be run before any mbuf allocations are done.
    */
   static void
   tunable_mbinit(void *dummy)
   {
           quad_t realmem;
   
           /*
            * The default limit for all mbuf related memory is 1/2 of all
            * available kernel memory (physical or kmem).
            * At most it can be 3/4 of available kernel memory.
            */
           realmem = qmin((quad_t)physmem * PAGE_SIZE, vm_kmem_size);
           maxmbufmem = realmem / 2;
           TUNABLE_QUAD_FETCH("kern.ipc.maxmbufmem", &maxmbufmem);
           if (maxmbufmem > realmem / 4 * 3)
                   maxmbufmem = realmem / 4 * 3;
   
           TUNABLE_INT_FETCH("kern.ipc.nmbclusters", &nmbclusters);
           if (nmbclusters == 0)
                   nmbclusters = maxmbufmem / MCLBYTES / 4;
   
           TUNABLE_INT_FETCH("kern.ipc.nmbjumbop", &nmbjumbop);
           if (nmbjumbop == 0)
                   nmbjumbop = maxmbufmem / MJUMPAGESIZE / 4;
   
           TUNABLE_INT_FETCH("kern.ipc.nmbjumbo9", &nmbjumbo9);
           if (nmbjumbo9 == 0)
                   nmbjumbo9 = maxmbufmem / MJUM9BYTES / 6;
   
           TUNABLE_INT_FETCH("kern.ipc.nmbjumbo16", &nmbjumbo16);
           if (nmbjumbo16 == 0)
                   nmbjumbo16 = maxmbufmem / MJUM16BYTES / 6;
   
           /*
            * We need at least as many mbufs as we have clusters of
            * the various types added together.
            */
           TUNABLE_INT_FETCH("kern.ipc.nmbufs", &nmbufs);
           if (nmbufs < nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16)
                   nmbufs = lmax(maxmbufmem / MSIZE / 5,
                       nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16);
   }
   SYSINIT(tunable_mbinit, SI_SUB_KMEM, SI_ORDER_MIDDLE, tunable_mbinit, NULL);
   
   static int
   sysctl_nmbclusters(SYSCTL_HANDLER_ARGS)
   {
           int error, newnmbclusters;
   
           newnmbclusters = nmbclusters;
           error = sysctl_handle_int(oidp, &newnmbclusters, 0, req);
           if (error == 0 && req->newptr && newnmbclusters != nmbclusters) {
                   if (newnmbclusters > nmbclusters &&
                       nmbufs >= nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16) {
                           nmbclusters = newnmbclusters;
                           nmbclusters = uma_zone_set_max(zone_clust, nmbclusters);
                           EVENTHANDLER_INVOKE(nmbclusters_change);
                   } else
                           error = EINVAL;
           }
           return (error);
   }
   SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbclusters, CTLTYPE_INT|CTLFLAG_RW,
   &nmbclusters, 0, sysctl_nmbclusters, "IU",
       "Maximum number of mbuf clusters allowed");
   
   static int
   sysctl_nmbjumbop(SYSCTL_HANDLER_ARGS)
   {
           int error, newnmbjumbop;
   
           newnmbjumbop = nmbjumbop;
           error = sysctl_handle_int(oidp, &newnmbjumbop, 0, req);
           if (error == 0 && req->newptr && newnmbjumbop != nmbjumbop) {
                   if (newnmbjumbop > nmbjumbop &&
                       nmbufs >= nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16) {
                           nmbjumbop = newnmbjumbop;
                           nmbjumbop = uma_zone_set_max(zone_jumbop, nmbjumbop);
                   } else
                           error = EINVAL;
           }
           return (error);
   }
   SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbjumbop, CTLTYPE_INT|CTLFLAG_RW,
   &nmbjumbop, 0, sysctl_nmbjumbop, "IU",
       "Maximum number of mbuf page size jumbo clusters allowed");
   
   static int
   sysctl_nmbjumbo9(SYSCTL_HANDLER_ARGS)
   {
           int error, newnmbjumbo9;
   
           newnmbjumbo9 = nmbjumbo9;
           error = sysctl_handle_int(oidp, &newnmbjumbo9, 0, req);
           if (error == 0 && req->newptr && newnmbjumbo9 != nmbjumbo9) {
                   if (newnmbjumbo9 > nmbjumbo9 &&
                       nmbufs >= nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16) {
                           nmbjumbo9 = newnmbjumbo9;
                           nmbjumbo9 = uma_zone_set_max(zone_jumbo9, nmbjumbo9);
                   } else
                           error = EINVAL;
           }
           return (error);
   }
   SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbjumbo9, CTLTYPE_INT|CTLFLAG_RW,
   &nmbjumbo9, 0, sysctl_nmbjumbo9, "IU",
       "Maximum number of mbuf 9k jumbo clusters allowed");
   
   static int
   sysctl_nmbjumbo16(SYSCTL_HANDLER_ARGS)
   {
           int error, newnmbjumbo16;
   
           newnmbjumbo16 = nmbjumbo16;
           error = sysctl_handle_int(oidp, &newnmbjumbo16, 0, req);
           if (error == 0 && req->newptr && newnmbjumbo16 != nmbjumbo16) {
                   if (newnmbjumbo16 > nmbjumbo16 &&
                       nmbufs >= nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16) {
                           nmbjumbo16 = newnmbjumbo16;
                           nmbjumbo16 = uma_zone_set_max(zone_jumbo16, nmbjumbo16);
                   } else
                           error = EINVAL;
           }
           return (error);
   }
   SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbjumbo16, CTLTYPE_INT|CTLFLAG_RW,
   &nmbjumbo16, 0, sysctl_nmbjumbo16, "IU",
       "Maximum number of mbuf 16k jumbo clusters allowed");
   
   static int
   sysctl_nmbufs(SYSCTL_HANDLER_ARGS)
   {
           int error, newnmbufs;
   
           newnmbufs = nmbufs;
           error = sysctl_handle_int(oidp, &newnmbufs, 0, req);
           if (error == 0 && req->newptr && newnmbufs != nmbufs) {
                   if (newnmbufs > nmbufs) {
                           nmbufs = newnmbufs;
                           nmbufs = uma_zone_set_max(zone_mbuf, nmbufs);
                           EVENTHANDLER_INVOKE(nmbufs_change);
                   } else
                           error = EINVAL;
           }
           return (error);
   }
   SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbufs, CTLTYPE_INT|CTLFLAG_RW,
   &nmbufs, 0, sysctl_nmbufs, "IU",
       "Maximum number of mbufs allowed");
   
   /*
    * Zones from which we allocate.
    */
   uma_zone_t      zone_mbuf;
   uma_zone_t      zone_clust;
   uma_zone_t      zone_pack;
   uma_zone_t      zone_jumbop;
   uma_zone_t      zone_jumbo9;
   uma_zone_t      zone_jumbo16;
   
   /*
    * Local prototypes.
    */
   static int      mb_ctor_mbuf(void *, int, void *, int);
   static int      mb_ctor_clust(void *, int, void *, int);
   static int      mb_ctor_pack(void *, int, void *, int);
   static void     mb_dtor_mbuf(void *, int, void *);
   static void     mb_dtor_pack(void *, int, void *);
   static int      mb_zinit_pack(void *, int, int);
   static void     mb_zfini_pack(void *, int);
   static void     mb_reclaim(uma_zone_t, int);
   static void    *mbuf_jumbo_alloc(uma_zone_t, vm_size_t, int, uint8_t *, int);
   
   /* Ensure that MSIZE is a power of 2. */
   CTASSERT((((MSIZE - 1) ^ MSIZE) + 1) >> 1 == MSIZE);
   
   /*
    * Initialize FreeBSD Network buffer allocation.
    */
   static void
   mbuf_init(void *dummy)
   {
   
           /*
            * Configure UMA zones for Mbufs, Clusters, and Packets.
            */
           zone_mbuf = uma_zcreate(MBUF_MEM_NAME, MSIZE,
               mb_ctor_mbuf, mb_dtor_mbuf,
   #ifdef INVARIANTS
               trash_init, trash_fini,
   #else
               NULL, NULL,
   #endif
               MSIZE - 1, UMA_ZONE_MAXBUCKET);
           if (nmbufs > 0)
                   nmbufs = uma_zone_set_max(zone_mbuf, nmbufs);
           uma_zone_set_warning(zone_mbuf, "kern.ipc.nmbufs limit reached");
           uma_zone_set_maxaction(zone_mbuf, mb_reclaim);
   
           zone_clust = uma_zcreate(MBUF_CLUSTER_MEM_NAME, MCLBYTES,
               mb_ctor_clust,
   #ifdef INVARIANTS
               trash_dtor, trash_init, trash_fini,
   #else
               NULL, NULL, NULL,
   #endif
               UMA_ALIGN_PTR, 0);
           if (nmbclusters > 0)
                   nmbclusters = uma_zone_set_max(zone_clust, nmbclusters);
           uma_zone_set_warning(zone_clust, "kern.ipc.nmbclusters limit reached");
           uma_zone_set_maxaction(zone_clust, mb_reclaim);
   
           zone_pack = uma_zsecond_create(MBUF_PACKET_MEM_NAME, mb_ctor_pack,
               mb_dtor_pack, mb_zinit_pack, mb_zfini_pack, zone_mbuf);
   
           /* Make jumbo frame zone too. Page size, 9k and 16k. */
           zone_jumbop = uma_zcreate(MBUF_JUMBOP_MEM_NAME, MJUMPAGESIZE,
               mb_ctor_clust,
   #ifdef INVARIANTS
               trash_dtor, trash_init, trash_fini,
   #else
               NULL, NULL, NULL,
   #endif
               UMA_ALIGN_PTR, 0);
           if (nmbjumbop > 0)
                   nmbjumbop = uma_zone_set_max(zone_jumbop, nmbjumbop);
           uma_zone_set_warning(zone_jumbop, "kern.ipc.nmbjumbop limit reached");
           uma_zone_set_maxaction(zone_jumbop, mb_reclaim);
   
           zone_jumbo9 = uma_zcreate(MBUF_JUMBO9_MEM_NAME, MJUM9BYTES,
               mb_ctor_clust,
   #ifdef INVARIANTS
               trash_dtor, trash_init, trash_fini,
   #else
               NULL, NULL, NULL,
   #endif
               UMA_ALIGN_PTR, 0);
           uma_zone_set_allocf(zone_jumbo9, mbuf_jumbo_alloc);
           if (nmbjumbo9 > 0)
                   nmbjumbo9 = uma_zone_set_max(zone_jumbo9, nmbjumbo9);
           uma_zone_set_warning(zone_jumbo9, "kern.ipc.nmbjumbo9 limit reached");
           uma_zone_set_maxaction(zone_jumbo9, mb_reclaim);
   
           zone_jumbo16 = uma_zcreate(MBUF_JUMBO16_MEM_NAME, MJUM16BYTES,
               mb_ctor_clust,
   #ifdef INVARIANTS
               trash_dtor, trash_init, trash_fini,
   #else
               NULL, NULL, NULL,
   #endif
               UMA_ALIGN_PTR, 0);
           uma_zone_set_allocf(zone_jumbo16, mbuf_jumbo_alloc);
           if (nmbjumbo16 > 0)
                   nmbjumbo16 = uma_zone_set_max(zone_jumbo16, nmbjumbo16);
           uma_zone_set_warning(zone_jumbo16, "kern.ipc.nmbjumbo16 limit reached");
           uma_zone_set_maxaction(zone_jumbo16, mb_reclaim);
   
           /*
            * Hook event handler for low-memory situation, used to
            * drain protocols and push data back to the caches (UMA
            * later pushes it back to VM).
            */
           EVENTHANDLER_REGISTER(vm_lowmem, mb_reclaim, NULL,
               EVENTHANDLER_PRI_FIRST);
   }
   SYSINIT(mbuf, SI_SUB_MBUF, SI_ORDER_FIRST, mbuf_init, NULL);
   
   #ifdef NETDUMP
   /*
    * netdump makes use of a pre-allocated pool of mbufs and clusters.  When
    * netdump is configured, we initialize a set of UMA cache zones which return
    * items from this pool.  At panic-time, the regular UMA zone pointers are
    * overwritten with those of the cache zones so that drivers may allocate and
    * free mbufs and clusters without attempting to allocate physical memory.
    *
    * We keep mbufs and clusters in a pair of mbuf queues.  In particular, for
    * the purpose of caching clusters, we treat them as mbufs.
    */
   static struct mbufq nd_mbufq =
       { STAILQ_HEAD_INITIALIZER(nd_mbufq.mq_head), 0, INT_MAX };
   static struct mbufq nd_clustq =
       { STAILQ_HEAD_INITIALIZER(nd_clustq.mq_head), 0, INT_MAX };
   
   static int nd_clsize;
   static uma_zone_t nd_zone_mbuf;
   static uma_zone_t nd_zone_clust;
   static uma_zone_t nd_zone_pack;
   
   static int
   nd_buf_import(void *arg, void **store, int count, int domain __unused,
       int flags)
   {
           struct mbufq *q;
           struct mbuf *m;
           int i;
   
           q = arg;
   
           for (i = 0; i < count; i++) {
                   m = mbufq_dequeue(q);
                   if (m == NULL)
                           break;
                   trash_init(m, q == &nd_mbufq ? MSIZE : nd_clsize, flags);
                   store[i] = m;
           }
           return (i);
   }
   
   static void
   nd_buf_release(void *arg, void **store, int count)
   {
           struct mbufq *q;
           struct mbuf *m;
           int i;
   
           q = arg;
   
           for (i = 0; i < count; i++) {
                   m = store[i];
                   (void)mbufq_enqueue(q, m);
           }
   }
   
   static int
   nd_pack_import(void *arg __unused, void **store, int count, int domain __unused,
       int flags __unused)
   {
           struct mbuf *m;
           void *clust;
           int i;
   
           for (i = 0; i < count; i++) {
                   m = m_get(MT_DATA, M_NOWAIT);
                   if (m == NULL)
                           break;
                   clust = uma_zalloc(nd_zone_clust, M_NOWAIT);
                   if (clust == NULL) {
                           m_free(m);
                           break;
                   }
                   mb_ctor_clust(clust, nd_clsize, m, 0);
                   store[i] = m;
           }
           return (i);
   }
   
   static void
   nd_pack_release(void *arg __unused, void **store, int count)
   {
           struct mbuf *m;
           void *clust;
           int i;
   
           for (i = 0; i < count; i++) {
                   m = store[i];
                   clust = m->m_ext.ext_buf;
                   uma_zfree(nd_zone_clust, clust);
                   uma_zfree(nd_zone_mbuf, m);
           }
   }
   
   /*
    * Free the pre-allocated mbufs and clusters reserved for netdump, and destroy
    * the corresponding UMA cache zones.
    */
   void
   netdump_mbuf_drain(void)
   {
           struct mbuf *m;
           void *item;
   
           if (nd_zone_mbuf != NULL) {
                   uma_zdestroy(nd_zone_mbuf);
                   nd_zone_mbuf = NULL;
           }
           if (nd_zone_clust != NULL) {
                   uma_zdestroy(nd_zone_clust);
                   nd_zone_clust = NULL;
           }
           if (nd_zone_pack != NULL) {
                   uma_zdestroy(nd_zone_pack);
                   nd_zone_pack = NULL;
           }
   
           while ((m = mbufq_dequeue(&nd_mbufq)) != NULL)
                   m_free(m);
           while ((item = mbufq_dequeue(&nd_clustq)) != NULL)
                   uma_zfree(m_getzone(nd_clsize), item);
   }
   
   /*
    * Callback invoked immediately prior to starting a netdump.
    */
   void
   netdump_mbuf_dump(void)
   {
   
           /*
            * All cluster zones return buffers of the size requested by the
            * drivers.  It's up to the driver to reinitialize the zones if the
            * MTU of a netdump-enabled interface changes.
            */
           printf("netdump: overwriting mbuf zone pointers\n");
           zone_mbuf = nd_zone_mbuf;
           zone_clust = nd_zone_clust;
           zone_pack = nd_zone_pack;
           zone_jumbop = nd_zone_clust;
           zone_jumbo9 = nd_zone_clust;
           zone_jumbo16 = nd_zone_clust;
   }
   
   /*
    * Reinitialize the netdump mbuf+cluster pool and cache zones.
    */
   void
   netdump_mbuf_reinit(int nmbuf, int nclust, int clsize)
   {
           struct mbuf *m;
           void *item;
   
           netdump_mbuf_drain();
   
           nd_clsize = clsize;
   
           nd_zone_mbuf = uma_zcache_create("netdump_" MBUF_MEM_NAME,
               MSIZE, mb_ctor_mbuf, mb_dtor_mbuf,
   #ifdef INVARIANTS
               trash_init, trash_fini,
   #else
               NULL, NULL,
   #endif
               nd_buf_import, nd_buf_release,
               &nd_mbufq, UMA_ZONE_NOBUCKET);
   
           nd_zone_clust = uma_zcache_create("netdump_" MBUF_CLUSTER_MEM_NAME,
               clsize, mb_ctor_clust,
   #ifdef INVARIANTS
               trash_dtor, trash_init, trash_fini,
   #else
               NULL, NULL, NULL,
   #endif
               nd_buf_import, nd_buf_release,
               &nd_clustq, UMA_ZONE_NOBUCKET);
   
           nd_zone_pack = uma_zcache_create("netdump_" MBUF_PACKET_MEM_NAME,
               MCLBYTES, mb_ctor_pack, mb_dtor_pack, NULL, NULL,
               nd_pack_import, nd_pack_release,
               NULL, UMA_ZONE_NOBUCKET);
   
           while (nmbuf-- > 0) {
                   m = m_get(MT_DATA, M_WAITOK);
                   uma_zfree(nd_zone_mbuf, m);
           }
           while (nclust-- > 0) {
                   item = uma_zalloc(m_getzone(nd_clsize), M_WAITOK);
                   uma_zfree(nd_zone_clust, item);
           }
   }
   #endif /* NETDUMP */
   
   /*
    * UMA backend page allocator for the jumbo frame zones.
    *
    * Allocates kernel virtual memory that is backed by contiguous physical
    * pages.
    */
   static void *
   mbuf_jumbo_alloc(uma_zone_t zone, vm_size_t bytes, int domain, uint8_t *flags,
       int wait)
   {
   
           /* Inform UMA that this allocator uses kernel_map/object. */
           *flags = UMA_SLAB_KERNEL;
           return ((void *)kmem_alloc_contig_domainset(DOMAINSET_FIXED(domain),
               bytes, wait, (vm_paddr_t)0, ~(vm_paddr_t)0, 1, 0,
               VM_MEMATTR_DEFAULT));
   }
   
   /*
    * Constructor for Mbuf master zone.
    *
    * The 'arg' pointer points to a mb_args structure which
    * contains call-specific information required to support the
    * mbuf allocation API.  See mbuf.h.
    */
   static int
   mb_ctor_mbuf(void *mem, int size, void *arg, int how)
   {
           struct mbuf *m;
           struct mb_args *args;
           int error;
           int flags;
           short type;
   
   #ifdef INVARIANTS
           trash_ctor(mem, size, arg, how);
   #endif
           args = (struct mb_args *)arg;
           type = args->type;
   
           /*
            * The mbuf is initialized later.  The caller has the
            * responsibility to set up any MAC labels too.
            */
           if (type == MT_NOINIT)
                   return (0);
   
           m = (struct mbuf *)mem;
           flags = args->flags;
           MPASS((flags & M_NOFREE) == 0);
   
           error = m_init(m, how, type, flags);
   
           return (error);
   }
   
   /*
    * The Mbuf master zone destructor.
    */
   static void
   mb_dtor_mbuf(void *mem, int size, void *arg)
   {
           struct mbuf *m;
           unsigned long flags;
   
           m = (struct mbuf *)mem;
           flags = (unsigned long)arg;
   
           KASSERT((m->m_flags & M_NOFREE) == 0, ("%s: M_NOFREE set", __func__));
           if (!(flags & MB_DTOR_SKIP) && (m->m_flags & M_PKTHDR) && !SLIST_EMPTY(&m->m_pkthdr.tags))
                   m_tag_delete_chain(m, NULL);
   #ifdef INVARIANTS
           trash_dtor(mem, size, arg);
   #endif
   }
   
   /*
    * The Mbuf Packet zone destructor.
    */
   static void
   mb_dtor_pack(void *mem, int size, void *arg)
   {
           struct mbuf *m;
   
           m = (struct mbuf *)mem;
           if ((m->m_flags & M_PKTHDR) != 0)
                   m_tag_delete_chain(m, NULL);
   
           /* Make sure we've got a clean cluster back. */
           KASSERT((m->m_flags & M_EXT) == M_EXT, ("%s: M_EXT not set", __func__));
           KASSERT(m->m_ext.ext_buf != NULL, ("%s: ext_buf == NULL", __func__));
           KASSERT(m->m_ext.ext_free == NULL, ("%s: ext_free != NULL", __func__));
           KASSERT(m->m_ext.ext_arg1 == NULL, ("%s: ext_arg1 != NULL", __func__));
           KASSERT(m->m_ext.ext_arg2 == NULL, ("%s: ext_arg2 != NULL", __func__));
           KASSERT(m->m_ext.ext_size == MCLBYTES, ("%s: ext_size != MCLBYTES", __func__));
           KASSERT(m->m_ext.ext_type == EXT_PACKET, ("%s: ext_type != EXT_PACKET", __func__));
   #ifdef INVARIANTS
           trash_dtor(m->m_ext.ext_buf, MCLBYTES, arg);
   #endif
           /*
            * If there are processes blocked on zone_clust, waiting for pages
            * to be freed up, * cause them to be woken up by draining the
            * packet zone.  We are exposed to a race here * (in the check for
            * the UMA_ZFLAG_FULL) where we might miss the flag set, but that
            * is deliberate. We don't want to acquire the zone lock for every
            * mbuf free.
            */
           if (uma_zone_exhausted_nolock(zone_clust))
                   zone_drain(zone_pack);
   }
   
   /*
    * The Cluster and Jumbo[PAGESIZE|9|16] zone constructor.
    *
    * Here the 'arg' pointer points to the Mbuf which we
    * are configuring cluster storage for.  If 'arg' is
    * empty we allocate just the cluster without setting
    * the mbuf to it.  See mbuf.h.
    */
   static int
   mb_ctor_clust(void *mem, int size, void *arg, int how)
   {
           struct mbuf *m;
   
   #ifdef INVARIANTS
           trash_ctor(mem, size, arg, how);
   #endif
           m = (struct mbuf *)arg;
           if (m != NULL) {
                   m->m_ext.ext_buf = (char *)mem;
                   m->m_data = m->m_ext.ext_buf;
                   m->m_flags |= M_EXT;
                   m->m_ext.ext_free = NULL;
                   m->m_ext.ext_arg1 = NULL;
                   m->m_ext.ext_arg2 = NULL;
                   m->m_ext.ext_size = size;
                   m->m_ext.ext_type = m_gettype(size);
                   m->m_ext.ext_flags = EXT_FLAG_EMBREF;
                   m->m_ext.ext_count = 1;
           }
   
           return (0);
   }
   
   /*
    * The Packet secondary zone's init routine, executed on the
    * object's transition from mbuf keg slab to zone cache.
    */
   static int
   mb_zinit_pack(void *mem, int size, int how)
   {
           struct mbuf *m;
   
           m = (struct mbuf *)mem;         /* m is virgin. */
           if (uma_zalloc_arg(zone_clust, m, how) == NULL ||
               m->m_ext.ext_buf == NULL)
                   return (ENOMEM);
           m->m_ext.ext_type = EXT_PACKET; /* Override. */
   #ifdef INVARIANTS
           trash_init(m->m_ext.ext_buf, MCLBYTES, how);
   #endif
           return (0);
   }
   
   /*
    * The Packet secondary zone's fini routine, executed on the
    * object's transition from zone cache to keg slab.
    */
   static void
   mb_zfini_pack(void *mem, int size)
   {
           struct mbuf *m;
   
           m = (struct mbuf *)mem;
   #ifdef INVARIANTS
           trash_fini(m->m_ext.ext_buf, MCLBYTES);
   #endif
           uma_zfree_arg(zone_clust, m->m_ext.ext_buf, NULL);
   #ifdef INVARIANTS
           trash_dtor(mem, size, NULL);
   #endif
   }
   
   /*
    * The "packet" keg constructor.
    */
   static int
   mb_ctor_pack(void *mem, int size, void *arg, int how)
   {
           struct mbuf *m;
           struct mb_args *args;
           int error, flags;
           short type;
   
           m = (struct mbuf *)mem;
           args = (struct mb_args *)arg;
           flags = args->flags;
           type = args->type;
           MPASS((flags & M_NOFREE) == 0);
   
   #ifdef INVARIANTS
           trash_ctor(m->m_ext.ext_buf, MCLBYTES, arg, how);
   #endif
   
           error = m_init(m, how, type, flags);
   
           /* m_ext is already initialized. */
           m->m_data = m->m_ext.ext_buf;
           m->m_flags = (flags | M_EXT);
   
           return (error);
   }
   
   /*
    * This is the protocol drain routine.  Called by UMA whenever any of the
    * mbuf zones is closed to its limit.
    *
    * No locks should be held when this is called.  The drain routines have to
    * presently acquire some locks which raises the possibility of lock order
    * reversal.
    */
   static void
   mb_reclaim(uma_zone_t zone __unused, int pending __unused)
   {
           struct domain *dp;
           struct protosw *pr;
   
           WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK | WARN_PANIC, NULL, __func__);
   
           for (dp = domains; dp != NULL; dp = dp->dom_next)
                   for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++)
                           if (pr->pr_drain != NULL)
                                   (*pr->pr_drain)();
   }
   
   /*
    * Clean up after mbufs with M_EXT storage attached to them if the
    * reference count hits 1.
    */
   void
   mb_free_ext(struct mbuf *m)
   {
           volatile u_int *refcnt;
           struct mbuf *mref;
           int freembuf;
   
           KASSERT(m->m_flags & M_EXT, ("%s: M_EXT not set on %p", __func__, m));
   
           /* See if this is the mbuf that holds the embedded refcount. */
           if (m->m_ext.ext_flags & EXT_FLAG_EMBREF) {
                   refcnt = &m->m_ext.ext_count;
                   mref = m;
           } else {
                   KASSERT(m->m_ext.ext_cnt != NULL,
                       ("%s: no refcounting pointer on %p", __func__, m));
                   refcnt = m->m_ext.ext_cnt;
                   mref = __containerof(refcnt, struct mbuf, m_ext.ext_count);
           }
   
           /*
            * Check if the header is embedded in the cluster.  It is
            * important that we can't touch any of the mbuf fields
            * after we have freed the external storage, since mbuf
            * could have been embedded in it.  For now, the mbufs
            * embedded into the cluster are always of type EXT_EXTREF,
            * and for this type we won't free the mref.
            */
           if (m->m_flags & M_NOFREE) {
                   freembuf = 0;
                   KASSERT(m->m_ext.ext_type == EXT_EXTREF,
                       ("%s: no-free mbuf %p has wrong type", __func__, m));
           } else
                   freembuf = 1;
   
           /* Free attached storage if this mbuf is the only reference to it. */
           if (*refcnt == 1 || atomic_fetchadd_int(refcnt, -1) == 1) {
                   switch (m->m_ext.ext_type) {
                   case EXT_PACKET:
                           /* The packet zone is special. */
                           if (*refcnt == 0)
                                   *refcnt = 1;
                           uma_zfree(zone_pack, mref);
                           break;
                   case EXT_CLUSTER:
                           uma_zfree(zone_clust, m->m_ext.ext_buf);
                           uma_zfree(zone_mbuf, mref);
                           break;
                   case EXT_JUMBOP:
                           uma_zfree(zone_jumbop, m->m_ext.ext_buf);
                           uma_zfree(zone_mbuf, mref);
                           break;
                   case EXT_JUMBO9:
                           uma_zfree(zone_jumbo9, m->m_ext.ext_buf);
                           uma_zfree(zone_mbuf, mref);
                           break;
                   case EXT_JUMBO16:
                           uma_zfree(zone_jumbo16, m->m_ext.ext_buf);
                           uma_zfree(zone_mbuf, mref);
                           break;
                   case EXT_SFBUF:
                   case EXT_NET_DRV:
                   case EXT_MOD_TYPE:
                   case EXT_DISPOSABLE:
                           KASSERT(mref->m_ext.ext_free != NULL,
                               ("%s: ext_free not set", __func__));
                           mref->m_ext.ext_free(mref);
                           uma_zfree(zone_mbuf, mref);
                           break;
                   case EXT_EXTREF:
                           KASSERT(m->m_ext.ext_free != NULL,
                               ("%s: ext_free not set", __func__));
                           m->m_ext.ext_free(m);
                           break;
                   default:
                           KASSERT(m->m_ext.ext_type == 0,
                               ("%s: unknown ext_type", __func__));
                   }
           }
   
           if (freembuf && m != mref)
                   uma_zfree(zone_mbuf, m);
   }
   
   /*
    * Official mbuf(9) allocation KPI for stack and drivers:
    *
    * m_get()      - a single mbuf without any attachments, sys/mbuf.h.
    * m_gethdr()   - a single mbuf initialized as M_PKTHDR, sys/mbuf.h.
    * m_getcl()    - an mbuf + 2k cluster, sys/mbuf.h.
    * m_clget()    - attach cluster to already allocated mbuf.
    * m_cljget()   - attach jumbo cluster to already allocated mbuf.
    * m_get2()     - allocate minimum mbuf that would fit size argument.
    * m_getm2()    - allocate a chain of mbufs/clusters.
    * m_extadd()   - attach external cluster to mbuf.
    *
    * m_free()     - free single mbuf with its tags and ext, sys/mbuf.h.
    * m_freem()    - free chain of mbufs.
    */
   
   int
   m_clget(struct mbuf *m, int how)
   {
   
           KASSERT((m->m_flags & M_EXT) == 0, ("%s: mbuf %p has M_EXT",
               __func__, m));
           m->m_ext.ext_buf = (char *)NULL;
           uma_zalloc_arg(zone_clust, m, how);
           /*
            * On a cluster allocation failure, drain the packet zone and retry,
            * we might be able to loosen a few clusters up on the drain.
            */
           if ((how & M_NOWAIT) && (m->m_ext.ext_buf == NULL)) {
                   zone_drain(zone_pack);
                   uma_zalloc_arg(zone_clust, m, how);
           }
           MBUF_PROBE2(m__clget, m, how);
           return (m->m_flags & M_EXT);
   }
   
   /*
    * m_cljget() is different from m_clget() as it can allocate clusters without
    * attaching them to an mbuf.  In that case the return value is the pointer
    * to the cluster of the requested size.  If an mbuf was specified, it gets
    * the cluster attached to it and the return value can be safely ignored.
    * For size it takes MCLBYTES, MJUMPAGESIZE, MJUM9BYTES, MJUM16BYTES.
    */
   void *
   m_cljget(struct mbuf *m, int how, int size)
   {
           uma_zone_t zone;
           void *retval;
   
           if (m != NULL) {
                   KASSERT((m->m_flags & M_EXT) == 0, ("%s: mbuf %p has M_EXT",
                       __func__, m));
                   m->m_ext.ext_buf = NULL;
           }
   
           zone = m_getzone(size);
           retval = uma_zalloc_arg(zone, m, how);
   
           MBUF_PROBE4(m__cljget, m, how, size, retval);
   
           return (retval);
   }
   
   /*
    * m_get2() allocates minimum mbuf that would fit "size" argument.
    */
   struct mbuf *
   m_get2(int size, int how, short type, int flags)
   {
           struct mb_args args;
           struct mbuf *m, *n;
   
           args.flags = flags;
           args.type = type;
   
           if (size <= MHLEN || (size <= MLEN && (flags & M_PKTHDR) == 0))
                   return (uma_zalloc_arg(zone_mbuf, &args, how));
           if (size <= MCLBYTES)
                   return (uma_zalloc_arg(zone_pack, &args, how));
   
           if (size > MJUMPAGESIZE)
                   return (NULL);
   
           m = uma_zalloc_arg(zone_mbuf, &args, how);
           if (m == NULL)
                   return (NULL);
   
           n = uma_zalloc_arg(zone_jumbop, m, how);
           if (n == NULL) {
                   uma_zfree(zone_mbuf, m);
                   return (NULL);
           }
   
           return (m);
   }
   
   /*
    * m_getjcl() returns an mbuf with a cluster of the specified size attached.
    * For size it takes MCLBYTES, MJUMPAGESIZE, MJUM9BYTES, MJUM16BYTES.
    */
  struct mbuf *
  m_getjcl(int how, short type, int flags, int size)
  {
          struct mb_args args;
          struct mbuf *m, *n;
          uma_zone_t zone;
  
          if (size == MCLBYTES)
                  return m_getcl(how, type, flags);
  
          args.flags = flags;
          args.type = type;
  
          m = uma_zalloc_arg(zone_mbuf, &args, how);
          if (m == NULL)
                  return (NULL);
  
          zone = m_getzone(size);
          n = uma_zalloc_arg(zone, m, how);
          if (n == NULL) {
                  uma_zfree(zone_mbuf, m);
                  return (NULL);
          }
          MBUF_PROBE5(m__getjcl, how, type, flags, size, m);
          return (m);
  }
  
  /*
   * 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 but still return the top of the newly allocated
   * chain.
   */
  struct mbuf *
  m_getm2(struct mbuf *m, int len, int how, short type, int flags)
  {
          struct mbuf *mb, *nm = NULL, *mtail = NULL;
  
          KASSERT(len >= 0, ("%s: len is < 0", __func__));
  
          /* Validate flags. */
          flags &= (M_PKTHDR | M_EOR);
  
          /* Packet header mbuf must be first in chain. */
          if ((flags & M_PKTHDR) && m != NULL)
                  flags &= ~M_PKTHDR;
  
          /* Loop and append maximum sized mbufs to the chain tail. */
          while (len > 0) {
                  if (len > MCLBYTES)
                          mb = m_getjcl(how, type, (flags & M_PKTHDR),
                              MJUMPAGESIZE);
                  else if (len >= MINCLSIZE)
                          mb = m_getcl(how, type, (flags & M_PKTHDR));
                  else if (flags & M_PKTHDR)
                          mb = m_gethdr(how, type);
                  else
                          mb = m_get(how, type);
  
                  /* Fail the whole operation if one mbuf can't be allocated. */
                  if (mb == NULL) {
                          if (nm != NULL)
                                  m_freem(nm);
                          return (NULL);
                  }
  
                  /* 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. */
          }
          if (flags & M_EOR)
                  mtail->m_flags |= M_EOR;  /* Only valid on the last mbuf. */
  
          /* 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;
                  mtail->m_flags &= ~M_EOR;
          } else
                  m = nm;
  
          return (m);
  }
  
  /*-
   * Configure a provided mbuf to refer to the provided external storage
   * buffer and setup a reference count for said buffer.
   *
   * Arguments:
   *    mb     The existing mbuf to which to attach the provided buffer.
   *    buf    The address of the provided external storage buffer.
   *    size   The size of the provided buffer.
   *    freef  A pointer to a routine that is responsible for freeing the
   *           provided external storage buffer.
   *    args   A pointer to an argument structure (of any type) to be passed
   *           to the provided freef routine (may be NULL).
   *    flags  Any other flags to be passed to the provided mbuf.
   *    type   The type that the external storage buffer should be
   *           labeled with.
   *
   * Returns:
   *    Nothing.
   */
  void
  m_extadd(struct mbuf *mb, char *buf, u_int size, m_ext_free_t freef,
      void *arg1, void *arg2, int flags, int type)
  {
  
          KASSERT(type != EXT_CLUSTER, ("%s: EXT_CLUSTER not allowed", __func__));
  
          mb->m_flags |= (M_EXT | flags);
          mb->m_ext.ext_buf = buf;
          mb->m_data = mb->m_ext.ext_buf;
          mb->m_ext.ext_size = size;
          mb->m_ext.ext_free = freef;
          mb->m_ext.ext_arg1 = arg1;
          mb->m_ext.ext_arg2 = arg2;
          mb->m_ext.ext_type = type;
  
          if (type != EXT_EXTREF) {
                  mb->m_ext.ext_count = 1;
                  mb->m_ext.ext_flags = EXT_FLAG_EMBREF;
          } else
                  mb->m_ext.ext_flags = 0;
  }
  
  /*
   * Free an entire chain of mbufs and associated external buffers, if
   * applicable.
   */
  void
  m_freem(struct mbuf *mb)
  {
  
          MBUF_PROBE1(m__freem, mb);
          while (mb != NULL)
                  mb = m_free(mb);
  }

Cache object: b1df12e754657add60ca55c79747dc48