The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*-
    2  * Copyright (c) 1997, Duke University
    3  * All rights reserved.
    4  *
    5  * Author:
    6  *         Andrew Gallatin <gallatin@cs.duke.edu>  
    7  *            
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  * 3. The name of Duke University may not be used to endorse or promote 
   17  *    products derived from this software without specific prior written 
   18  *    permission.
   19  * 
   20  * THIS SOFTWARE IS PROVIDED BY DUKE UNIVERSITY ``AS IS'' AND ANY
   21  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   23  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL DUKE UNIVERSITY BE LIABLE
   24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
   25  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
   26  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITSOR BUSINESS
   27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
   28  * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
   29  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
   30  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
   31  *
   32  * $FreeBSD: releng/5.0/sys/kern/uipc_cow.c 104908 2002-10-11 14:58:34Z mike $
   33  */
   34 /*
   35  * This is a set of routines for enabling and disabling copy on write
   36  * protection for data written into sockets.
   37  */
   38 
   39 #include <sys/param.h>
   40 #include <sys/systm.h>
   41 #include <sys/kernel.h>
   42 #include <sys/proc.h>
   43 #include <sys/lock.h>
   44 #include <sys/mutex.h>
   45 #include <sys/mbuf.h>
   46 #include <sys/socketvar.h>
   47 #include <sys/uio.h>
   48 
   49 #include <vm/vm.h>
   50 #include <vm/vm_param.h>
   51 #include <vm/pmap.h>
   52 #include <vm/vm_map.h>
   53 #include <vm/vm_page.h>
   54 #include <vm/vm_object.h>
   55 #if 0
   56 #include <vm/vm_pager.h>
   57 #include <vm/vm_kern.h>
   58 #include <vm/vm_extern.h>
   59 #include <vm/vm_zone.h>
   60 #include <vm/swap_pager.h>
   61 #endif
   62 
   63 
   64 struct netsend_cow_stats {
   65         int attempted;
   66         int fail_not_mapped;
   67         int fail_wired;
   68         int fail_not_anon;
   69         int fail_pmap_cow;
   70         int fail_pg_error;
   71         int fail_kva;
   72         int free_post_exit;
   73         int success;
   74         int iodone;
   75         int freed;
   76 };
   77 
   78 static struct netsend_cow_stats socow_stats = {0,0,0,0,0,0,0,0,0,0,0};
   79 
   80 extern struct sf_buf *sf_bufs;
   81 extern vm_offset_t sf_base;
   82 #define dtosf(x) (&sf_bufs[((uintptr_t)(x) - (uintptr_t)sf_base) >> PAGE_SHIFT])
   83 static void socow_iodone(void *addr, void *args);
   84 
   85 static void
   86 socow_iodone(void *addr, void *args)
   87 {       
   88         int s;
   89         struct sf_buf *sf;
   90 
   91         vm_offset_t paddr; 
   92         vm_page_t pp;
   93 
   94         sf = dtosf(addr);
   95         paddr = vtophys((vm_offset_t)addr);
   96         pp = PHYS_TO_VM_PAGE(paddr);
   97         s = splvm();
   98         /* remove COW mapping  */
   99         vm_page_lock_queues();
  100         vm_page_cowclear(pp);
  101         vm_page_unlock_queues();
  102         vm_object_deallocate(pp->object);
  103         splx(s);
  104         /* note that sf_buf_free() unwires the page for us*/
  105         sf_buf_free(addr, NULL);
  106         socow_stats.iodone++;
  107 }
  108 
  109 int
  110 socow_setup(struct mbuf *m0, struct uio *uio)
  111 {
  112         struct sf_buf *sf;
  113         vm_page_t pp;
  114         vm_offset_t pa;
  115         struct iovec *iov;
  116         struct vmspace *vmspace;
  117         struct vm_map *map;
  118         vm_offset_t uva;
  119         int s;
  120 
  121         vmspace = curproc->p_vmspace;;
  122         map = &vmspace->vm_map;
  123         uva = (vm_offset_t) uio->uio_iov->iov_base;
  124 
  125         s = splvm();
  126 
  127        /* 
  128         * verify page is mapped & not already wired for i/o
  129         */
  130         socow_stats.attempted++;
  131         pa=pmap_extract(map->pmap, uva);
  132         if(!pa) {
  133                 socow_stats.fail_not_mapped++;
  134                 splx(s);
  135                 return(0);
  136         }
  137         pp = PHYS_TO_VM_PAGE(pa);
  138 
  139         sf = sf_buf_alloc();
  140         sf->m = pp;
  141         pmap_qenter(sf->kva, &pp, 1);
  142 
  143         /* 
  144          * set up COW
  145          */
  146         vm_page_lock_queues();
  147         vm_page_cowsetup(pp);
  148 
  149         /*
  150          * wire the page for I/O
  151          */
  152         vm_page_wire(pp);
  153         vm_page_unlock_queues();
  154 
  155         /*
  156          * prevent the process from exiting on us.
  157          */
  158         vm_object_reference(pp->object);
  159 
  160         /* 
  161          * attach to mbuf
  162          */
  163         m0->m_data = (caddr_t)sf->kva;
  164         m0->m_len = PAGE_SIZE;
  165         MEXTADD(m0, sf->kva, PAGE_SIZE, socow_iodone, NULL, 0, EXT_SFBUF);
  166         socow_stats.success++;
  167 
  168         iov = uio->uio_iov;
  169         iov->iov_base = (char *)iov->iov_base + PAGE_SIZE;
  170         iov->iov_len -= PAGE_SIZE;
  171         uio->uio_resid -= PAGE_SIZE;
  172         uio->uio_offset += PAGE_SIZE;
  173         if (iov->iov_len == 0) {
  174                 uio->uio_iov++;
  175                 uio->uio_iovcnt--;
  176         }
  177 
  178         splx(s);
  179         return(1);
  180 }

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