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

     /*-
      * Copyright (c) 1997, Duke University
      * All rights reserved.
      *
      * Author:
      *         Andrew Gallatin <gallatin@cs.duke.edu>  
      *            
      * 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, 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.
     * 3. The name of Duke University may not be used to endorse or promote 
     *    products derived from this software without specific prior written 
     *    permission.
     * 
     * THIS SOFTWARE IS PROVIDED BY DUKE UNIVERSITY ``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 DUKE UNIVERSITY 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 PROFITSOR 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.  
     */
    
    /*
     * This is a set of routines for enabling and disabling copy on write
     * protection for data written into sockets.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/5.2/sys/kern/uipc_cow.c 122780 2003-11-16 06:11:26Z alc $");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kernel.h>
    #include <sys/proc.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/mbuf.h>
    #include <sys/sf_buf.h>
    #include <sys/socketvar.h>
    #include <sys/uio.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/pmap.h>
    #include <vm/vm_map.h>
    #include <vm/vm_page.h>
    #include <vm/vm_object.h>
    
    
    struct netsend_cow_stats {
            int attempted;
            int fail_not_mapped;
            int fail_wired;
            int fail_not_anon;
            int fail_pmap_cow;
            int fail_pg_error;
            int fail_kva;
            int free_post_exit;
            int success;
            int iodone;
            int freed;
    };
    
    static struct netsend_cow_stats socow_stats = {0,0,0,0,0,0,0,0,0,0,0};
    
    static void socow_iodone(void *addr, void *args);
    
    static void
    socow_iodone(void *addr, void *args)
    {       
            int s;
            struct sf_buf *sf;
            vm_page_t pp;
    
            sf = args;
            pp = sf_buf_page(sf);
            s = splvm();
            /* remove COW mapping  */
            vm_page_lock_queues();
            vm_page_cowclear(pp);
            vm_page_unlock_queues();
            splx(s);
            /* note that sf_buf_free() unwires the page for us*/
            sf_buf_free(addr, args);
            socow_stats.iodone++;
    }
    
    int
    socow_setup(struct mbuf *m0, struct uio *uio)
   {
           struct sf_buf *sf;
           vm_page_t pp;
           vm_paddr_t pa;
           struct iovec *iov;
           struct vmspace *vmspace;
           struct vm_map *map;
           vm_offset_t uva;
           int s;
   
           vmspace = curproc->p_vmspace;
           map = &vmspace->vm_map;
           uva = (vm_offset_t) uio->uio_iov->iov_base;
   
           s = splvm();
   
          /* 
           * verify page is mapped & not already wired for i/o
           */
           socow_stats.attempted++;
           pa=pmap_extract(map->pmap, uva);
           if(!pa) {
                   socow_stats.fail_not_mapped++;
                   splx(s);
                   return(0);
           }
           pp = PHYS_TO_VM_PAGE(pa);
   
           /* 
            * set up COW
            */
           vm_page_lock_queues();
           vm_page_cowsetup(pp);
   
           /*
            * wire the page for I/O
            */
           vm_page_wire(pp);
           vm_page_unlock_queues();
   
           /*
            * Allocate an sf buf
            */
           sf = sf_buf_alloc(pp);
   
           /* 
            * attach to mbuf
            */
           m0->m_data = (caddr_t)sf_buf_kva(sf);
           m0->m_len = PAGE_SIZE;
           MEXTADD(m0, sf_buf_kva(sf), PAGE_SIZE, socow_iodone, sf, M_RDONLY,
               EXT_SFBUF);
           socow_stats.success++;
   
           iov = uio->uio_iov;
           iov->iov_base = (char *)iov->iov_base + PAGE_SIZE;
           iov->iov_len -= PAGE_SIZE;
           uio->uio_resid -= PAGE_SIZE;
           uio->uio_offset += PAGE_SIZE;
           if (iov->iov_len == 0) {
                   uio->uio_iov++;
                   uio->uio_iovcnt--;
           }
   
           splx(s);
           return(1);
   }

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