xref: /freebsd/sys/vm/phys_pager.c (revision 42c159fe388a3765f69860c84183700af37aca8a)
1 /*
2  * Copyright (c) 2000 Peter Wemm
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  * 1. Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  * 2. Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  *
13  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23  * SUCH DAMAGE.
24  *
25  * $FreeBSD$
26  */
27 
28 #include <sys/param.h>
29 #include <sys/systm.h>
30 #include <sys/linker_set.h>
31 #include <sys/conf.h>
32 #include <sys/kernel.h>
33 #include <sys/lock.h>
34 #include <sys/proc.h>
35 #include <sys/mutex.h>
36 #include <sys/mman.h>
37 #include <sys/sysctl.h>
38 
39 #include <vm/vm.h>
40 #include <vm/vm_object.h>
41 #include <vm/vm_page.h>
42 #include <vm/vm_pager.h>
43 
44 /* prevent concurrant creation races */
45 static int phys_pager_alloc_lock;
46 /* list of device pager objects */
47 static struct pagerlst phys_pager_object_list;
48 /* protect access to phys_pager_object_list */
49 static struct mtx phys_pager_mtx;
50 
51 static void
52 phys_pager_init(void)
53 {
54 
55 	TAILQ_INIT(&phys_pager_object_list);
56 	mtx_init(&phys_pager_mtx, "phys_pager list", MTX_DEF);
57 }
58 
59 static vm_object_t
60 phys_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
61 		 vm_ooffset_t foff)
62 {
63 	vm_object_t object;
64 
65 	GIANT_REQUIRED;
66 
67 	/*
68 	 * Offset should be page aligned.
69 	 */
70 	if (foff & PAGE_MASK)
71 		return (NULL);
72 
73 	size = round_page(size);
74 
75 	if (handle != NULL) {
76 		/*
77 		 * Lock to prevent object creation race condition.
78 		 */
79 		while (phys_pager_alloc_lock) {
80 			phys_pager_alloc_lock = -1;
81 			tsleep(&phys_pager_alloc_lock, PVM, "swpalc", 0);
82 		}
83 		phys_pager_alloc_lock = 1;
84 
85 		/*
86 		 * Look up pager, creating as necessary.
87 		 */
88 		object = vm_pager_object_lookup(&phys_pager_object_list, handle);
89 		if (object == NULL) {
90 			/*
91 			 * Allocate object and associate it with the pager.
92 			 */
93 			object = vm_object_allocate(OBJT_PHYS,
94 				OFF_TO_IDX(foff + size));
95 			object->handle = handle;
96 			mtx_lock(&phys_pager_mtx);
97 			TAILQ_INSERT_TAIL(&phys_pager_object_list, object,
98 			    pager_object_list);
99 			mtx_unlock(&phys_pager_mtx);
100 		} else {
101 			/*
102 			 * Gain a reference to the object.
103 			 */
104 			vm_object_reference(object);
105 			if (OFF_TO_IDX(foff + size) > object->size)
106 				object->size = OFF_TO_IDX(foff + size);
107 		}
108 		if (phys_pager_alloc_lock == -1)
109 			wakeup(&phys_pager_alloc_lock);
110 		phys_pager_alloc_lock = 0;
111 
112 	} else {
113 		object = vm_object_allocate(OBJT_PHYS,
114 			OFF_TO_IDX(foff + size));
115 	}
116 
117 	return (object);
118 }
119 
120 static void
121 phys_pager_dealloc(vm_object_t object)
122 {
123 
124 	if (object->handle != NULL) {
125 		mtx_lock(&phys_pager_mtx);
126 		TAILQ_REMOVE(&phys_pager_object_list, object, pager_object_list);
127 		mtx_unlock(&phys_pager_mtx);
128 	}
129 }
130 
131 static int
132 phys_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage)
133 {
134 	int i, s;
135 
136 	s = splvm();
137 	/*
138 	 * Fill as many pages as vm_fault has allocated for us.
139 	 */
140 	for (i = 0; i < count; i++) {
141 		if ((m[i]->flags & PG_ZERO) == 0)
142 			vm_page_zero_fill(m[i]);
143 		vm_page_flag_set(m[i], PG_ZERO);
144 		/* Switch off pv_entries */
145 		vm_page_unmanage(m[i]);
146 		m[i]->valid = VM_PAGE_BITS_ALL;
147 		m[i]->dirty = 0;
148 		/* The requested page must remain busy, the others not. */
149 		if (reqpage != i) {
150 			vm_page_flag_clear(m[i], PG_BUSY);
151 			m[i]->busy = 0;
152 		}
153 	}
154 	splx(s);
155 
156 	return (VM_PAGER_OK);
157 }
158 
159 static void
160 phys_pager_putpages(vm_object_t object, vm_page_t *m, int count, boolean_t sync,
161 		    int *rtvals)
162 {
163 
164 	panic("phys_pager_putpage called");
165 }
166 
167 /*
168  * Implement a pretty aggressive clustered getpages strategy.  Hint that
169  * everything in an entire 4MB window should be prefaulted at once.
170  *
171  * XXX 4MB (1024 slots per page table page) is convenient for x86,
172  * but may not be for other arches.
173  */
174 #ifndef PHYSCLUSTER
175 #define PHYSCLUSTER 1024
176 #endif
177 static boolean_t
178 phys_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
179 		   int *after)
180 {
181 	vm_pindex_t base, end;
182 
183 	base = pindex & (~(PHYSCLUSTER - 1));
184 	end = base + (PHYSCLUSTER - 1);
185 	if (before != NULL)
186 		*before = pindex - base;
187 	if (after != NULL)
188 		*after = end - pindex;
189 	return (TRUE);
190 }
191 
192 struct pagerops physpagerops = {
193 	phys_pager_init,
194 	phys_pager_alloc,
195 	phys_pager_dealloc,
196 	phys_pager_getpages,
197 	phys_pager_putpages,
198 	phys_pager_haspage,
199 	NULL
200 };
201