FreeBSD/Linux Kernel Cross Reference
sys/kern/uipc_cow.c
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
33 /*
34 * This is a set of routines for enabling and disabling copy on write
35 * protection for data written into sockets.
36 */
37
38 #include <sys/cdefs.h>
39 __FBSDID("$FreeBSD$");
40
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/kernel.h>
44 #include <sys/proc.h>
45 #include <sys/lock.h>
46 #include <sys/mutex.h>
47 #include <sys/mbuf.h>
48 #include <sys/sf_buf.h>
49 #include <sys/socketvar.h>
50 #include <sys/uio.h>
51
52 #include <vm/vm.h>
53 #include <vm/vm_param.h>
54 #include <vm/pmap.h>
55 #include <vm/vm_map.h>
56 #include <vm/vm_page.h>
57 #include <vm/vm_object.h>
58
59
60 struct netsend_cow_stats {
61 int attempted;
62 int fail_not_mapped;
63 int fail_sf_buf;
64 int success;
65 int iodone;
66 };
67
68 static struct netsend_cow_stats socow_stats;
69
70 static void socow_iodone(void *addr, void *args);
71
72 static void
73 socow_iodone(void *addr, void *args)
74 {
75 struct sf_buf *sf;
76 vm_page_t pp;
77
78 sf = args;
79 pp = sf_buf_page(sf);
80 sf_buf_free(sf);
81 /* remove COW mapping */
82 vm_page_lock_queues();
83 vm_page_cowclear(pp);
84 vm_page_unwire(pp, 0);
85 /*
86 * Check for the object going away on us. This can
87 * happen since we don't hold a reference to it.
88 * If so, we're responsible for freeing the page.
89 */
90 if (pp->wire_count == 0 && pp->object == NULL)
91 vm_page_free(pp);
92 vm_page_unlock_queues();
93 socow_stats.iodone++;
94 }
95
96 int
97 socow_setup(struct mbuf *m0, struct uio *uio)
98 {
99 struct sf_buf *sf;
100 vm_page_t pp;
101 vm_paddr_t pa;
102 struct iovec *iov;
103 struct vmspace *vmspace;
104 struct vm_map *map;
105 vm_offset_t uva;
106 int s;
107
108 vmspace = curproc->p_vmspace;
109 map = &vmspace->vm_map;
110 uva = (vm_offset_t) uio->uio_iov->iov_base;
111
112 s = splvm();
113
114 /*
115 * verify page is mapped & not already wired for i/o
116 */
117 socow_stats.attempted++;
118 pa=pmap_extract(map->pmap, uva);
119 if(!pa) {
120 socow_stats.fail_not_mapped++;
121 splx(s);
122 return(0);
123 }
124 pp = PHYS_TO_VM_PAGE(pa);
125
126 /*
127 * set up COW
128 */
129 vm_page_lock_queues();
130 vm_page_cowsetup(pp);
131
132 /*
133 * wire the page for I/O
134 */
135 vm_page_wire(pp);
136 vm_page_unlock_queues();
137
138 /*
139 * Allocate an sf buf
140 */
141 sf = sf_buf_alloc(pp, SFB_CATCH);
142 if (!sf) {
143 vm_page_lock_queues();
144 vm_page_cowclear(pp);
145 vm_page_unwire(pp, 0);
146 /*
147 * Check for the object going away on us. This can
148 * happen since we don't hold a reference to it.
149 * If so, we're responsible for freeing the page.
150 */
151 if (pp->wire_count == 0 && pp->object == NULL)
152 vm_page_free(pp);
153 vm_page_unlock_queues();
154 socow_stats.fail_sf_buf++;
155 splx(s);
156 return(0);
157 }
158 /*
159 * attach to mbuf
160 */
161 m0->m_data = (caddr_t)sf_buf_kva(sf);
162 m0->m_len = PAGE_SIZE;
163 MEXTADD(m0, sf_buf_kva(sf), PAGE_SIZE, socow_iodone, sf, M_RDONLY,
164 EXT_SFBUF);
165 socow_stats.success++;
166
167 iov = uio->uio_iov;
168 iov->iov_base = (char *)iov->iov_base + PAGE_SIZE;
169 iov->iov_len -= PAGE_SIZE;
170 uio->uio_resid -= PAGE_SIZE;
171 uio->uio_offset += PAGE_SIZE;
172 if (iov->iov_len == 0) {
173 uio->uio_iov++;
174 uio->uio_iovcnt--;
175 }
176
177 splx(s);
178 return(1);
179 }
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