FreeBSD/Linux Kernel Cross Reference
sys/vm/sg_pager.c
1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3 *
4 * Copyright (c) 2009 Hudson River Trading LLC
5 * Written by: John H. Baldwin <jhb@FreeBSD.org>
6 * All rights reserved.
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 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #include <sys/cdefs.h>
31 __FBSDID("$FreeBSD$");
32
33 /*
34 * This pager manages OBJT_SG objects. These objects are backed by
35 * a scatter/gather list of physical address ranges.
36 */
37
38 #include <sys/param.h>
39 #include <sys/lock.h>
40 #include <sys/mutex.h>
41 #include <sys/rwlock.h>
42 #include <sys/sglist.h>
43 #include <sys/vmmeter.h>
44
45 #include <vm/vm.h>
46 #include <vm/vm_param.h>
47 #include <vm/vm_object.h>
48 #include <vm/vm_page.h>
49 #include <vm/vm_pager.h>
50 #include <vm/vm_phys.h>
51 #include <vm/uma.h>
52
53 static vm_object_t sg_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
54 vm_ooffset_t, struct ucred *);
55 static void sg_pager_dealloc(vm_object_t);
56 static int sg_pager_getpages(vm_object_t, vm_page_t *, int, int *, int *);
57 static void sg_pager_putpages(vm_object_t, vm_page_t *, int,
58 boolean_t, int *);
59 static boolean_t sg_pager_haspage(vm_object_t, vm_pindex_t, int *,
60 int *);
61
62 struct pagerops sgpagerops = {
63 .pgo_alloc = sg_pager_alloc,
64 .pgo_dealloc = sg_pager_dealloc,
65 .pgo_getpages = sg_pager_getpages,
66 .pgo_putpages = sg_pager_putpages,
67 .pgo_haspage = sg_pager_haspage,
68 };
69
70 static vm_object_t
71 sg_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
72 vm_ooffset_t foff, struct ucred *cred)
73 {
74 struct sglist *sg;
75 vm_object_t object;
76 vm_pindex_t npages, pindex;
77 int i;
78
79 /*
80 * Offset should be page aligned.
81 */
82 if (foff & PAGE_MASK)
83 return (NULL);
84
85 /*
86 * The scatter/gather list must only include page-aligned
87 * ranges.
88 */
89 npages = 0;
90 sg = handle;
91 for (i = 0; i < sg->sg_nseg; i++) {
92 if ((sg->sg_segs[i].ss_paddr % PAGE_SIZE) != 0 ||
93 (sg->sg_segs[i].ss_len % PAGE_SIZE) != 0)
94 return (NULL);
95 npages += sg->sg_segs[i].ss_len / PAGE_SIZE;
96 }
97
98 /*
99 * The scatter/gather list has a fixed size. Refuse requests
100 * to map beyond that.
101 */
102 size = round_page(size);
103 pindex = OFF_TO_IDX(foff) + OFF_TO_IDX(size);
104 if (pindex > npages || pindex < OFF_TO_IDX(foff) ||
105 pindex < OFF_TO_IDX(size))
106 return (NULL);
107
108 /*
109 * Allocate a new object and associate it with the
110 * scatter/gather list. It is ok for our purposes to have
111 * multiple VM objects associated with the same scatter/gather
112 * list because scatter/gather lists are static. This is also
113 * simpler than ensuring a unique object per scatter/gather
114 * list.
115 */
116 object = vm_object_allocate(OBJT_SG, npages);
117 object->handle = sglist_hold(sg);
118 TAILQ_INIT(&object->un_pager.sgp.sgp_pglist);
119 return (object);
120 }
121
122 static void
123 sg_pager_dealloc(vm_object_t object)
124 {
125 struct sglist *sg;
126 vm_page_t m;
127
128 /*
129 * Free up our fake pages.
130 */
131 while ((m = TAILQ_FIRST(&object->un_pager.sgp.sgp_pglist)) != 0) {
132 if (vm_page_busy_acquire(m, VM_ALLOC_WAITFAIL) == 0)
133 continue;
134 TAILQ_REMOVE(&object->un_pager.sgp.sgp_pglist, m, plinks.q);
135 vm_page_putfake(m);
136 }
137
138 sg = object->handle;
139 sglist_free(sg);
140 object->handle = NULL;
141 object->type = OBJT_DEAD;
142 }
143
144 static int
145 sg_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
146 int *rahead)
147 {
148 struct sglist *sg;
149 vm_page_t m_paddr, page;
150 vm_pindex_t offset;
151 vm_paddr_t paddr;
152 vm_memattr_t memattr;
153 size_t space;
154 int i;
155
156 /* Since our haspage reports zero after/before, the count is 1. */
157 KASSERT(count == 1, ("%s: count %d", __func__, count));
158 /* Handle is stable while paging is in progress. */
159 sg = object->handle;
160 memattr = object->memattr;
161 offset = m[0]->pindex;
162
163 /*
164 * Lookup the physical address of the requested page. An initial
165 * value of '1' instead of '' is used so we can assert that the
166 * page is found since '' can be a valid page-aligned physical
167 * address.
168 */
169 space = 0;
170 paddr = 1;
171 for (i = 0; i < sg->sg_nseg; i++) {
172 if (space + sg->sg_segs[i].ss_len <= (offset * PAGE_SIZE)) {
173 space += sg->sg_segs[i].ss_len;
174 continue;
175 }
176 paddr = sg->sg_segs[i].ss_paddr + offset * PAGE_SIZE - space;
177 break;
178 }
179 KASSERT(paddr != 1, ("invalid SG page index"));
180
181 /* If "paddr" is a real page, perform a sanity check on "memattr". */
182 if ((m_paddr = vm_phys_paddr_to_vm_page(paddr)) != NULL &&
183 pmap_page_get_memattr(m_paddr) != memattr) {
184 memattr = pmap_page_get_memattr(m_paddr);
185 printf(
186 "WARNING: A device driver has set \"memattr\" inconsistently.\n");
187 }
188
189 /* Return a fake page for the requested page. */
190 KASSERT(!(m[0]->flags & PG_FICTITIOUS),
191 ("backing page for SG is fake"));
192
193 /* Construct a new fake page. */
194 page = vm_page_getfake(paddr, memattr);
195 VM_OBJECT_WLOCK(object);
196 TAILQ_INSERT_TAIL(&object->un_pager.sgp.sgp_pglist, page, plinks.q);
197 vm_page_replace(page, object, offset, m[0]);
198 VM_OBJECT_WUNLOCK(object);
199 m[0] = page;
200 vm_page_valid(page);
201
202 if (rbehind)
203 *rbehind = 0;
204 if (rahead)
205 *rahead = 0;
206
207 return (VM_PAGER_OK);
208 }
209
210 static void
211 sg_pager_putpages(vm_object_t object, vm_page_t *m, int count,
212 boolean_t sync, int *rtvals)
213 {
214
215 panic("sg_pager_putpage called");
216 }
217
218 static boolean_t
219 sg_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
220 int *after)
221 {
222
223 if (before != NULL)
224 *before = 0;
225 if (after != NULL)
226 *after = 0;
227 return (TRUE);
228 }
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