|
1 |
/*
|
|
2 |
* L2/refcount table cache for the QCOW2 format
|
|
3 |
*
|
|
4 |
* Copyright (c) 2010 Kevin Wolf <kwolf@redhat.com>
|
|
5 |
*
|
|
6 |
* Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
7 |
* of this software and associated documentation files (the "Software"), to deal
|
|
8 |
* in the Software without restriction, including without limitation the rights
|
|
9 |
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
10 |
* copies of the Software, and to permit persons to whom the Software is
|
|
11 |
* furnished to do so, subject to the following conditions:
|
|
12 |
*
|
|
13 |
* The above copyright notice and this permission notice shall be included in
|
|
14 |
* all copies or substantial portions of the Software.
|
|
15 |
*
|
|
16 |
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
17 |
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
18 |
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
|
|
19 |
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
20 |
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
21 |
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
|
22 |
* THE SOFTWARE.
|
|
23 |
*/
|
|
24 |
|
|
25 |
#include "block_int.h"
|
|
26 |
#include "qemu-common.h"
|
|
27 |
#include "qcow2.h"
|
|
28 |
|
|
29 |
typedef struct Qcow2CachedTable {
|
|
30 |
void* table;
|
|
31 |
int64_t offset;
|
|
32 |
bool dirty;
|
|
33 |
int cache_hits;
|
|
34 |
int ref;
|
|
35 |
} Qcow2CachedTable;
|
|
36 |
|
|
37 |
struct Qcow2Cache {
|
|
38 |
int size;
|
|
39 |
Qcow2CachedTable* entries;
|
|
40 |
struct Qcow2Cache* depends;
|
|
41 |
bool writethrough;
|
|
42 |
};
|
|
43 |
|
|
44 |
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables,
|
|
45 |
bool writethrough)
|
|
46 |
{
|
|
47 |
BDRVQcowState *s = bs->opaque;
|
|
48 |
Qcow2Cache *c;
|
|
49 |
int i;
|
|
50 |
|
|
51 |
c = qemu_mallocz(sizeof(*c));
|
|
52 |
c->size = num_tables;
|
|
53 |
c->entries = qemu_mallocz(sizeof(*c->entries) * num_tables);
|
|
54 |
c->writethrough = writethrough;
|
|
55 |
|
|
56 |
for (i = 0; i < c->size; i++) {
|
|
57 |
c->entries[i].table = qemu_blockalign(bs, s->cluster_size);
|
|
58 |
}
|
|
59 |
|
|
60 |
return c;
|
|
61 |
}
|
|
62 |
|
|
63 |
int qcow2_cache_destroy(BlockDriverState* bs, Qcow2Cache *c)
|
|
64 |
{
|
|
65 |
int i;
|
|
66 |
|
|
67 |
for (i = 0; i < c->size; i++) {
|
|
68 |
assert(c->entries[i].ref == 0);
|
|
69 |
qemu_vfree(c->entries[i].table);
|
|
70 |
}
|
|
71 |
|
|
72 |
qemu_free(c->entries);
|
|
73 |
qemu_free(c);
|
|
74 |
|
|
75 |
return 0;
|
|
76 |
}
|
|
77 |
|
|
78 |
static int qcow2_cache_flush_dependency(BlockDriverState *bs, Qcow2Cache *c)
|
|
79 |
{
|
|
80 |
int ret;
|
|
81 |
|
|
82 |
ret = qcow2_cache_flush(bs, c->depends);
|
|
83 |
if (ret < 0) {
|
|
84 |
return ret;
|
|
85 |
}
|
|
86 |
|
|
87 |
c->depends = NULL;
|
|
88 |
return 0;
|
|
89 |
}
|
|
90 |
|
|
91 |
static int qcow2_cache_entry_flush(BlockDriverState *bs, Qcow2Cache *c, int i)
|
|
92 |
{
|
|
93 |
BDRVQcowState *s = bs->opaque;
|
|
94 |
int ret;
|
|
95 |
|
|
96 |
if (!c->entries[i].dirty || !c->entries[i].offset) {
|
|
97 |
return 0;
|
|
98 |
}
|
|
99 |
|
|
100 |
if (c->depends) {
|
|
101 |
ret = qcow2_cache_flush_dependency(bs, c);
|
|
102 |
if (ret < 0) {
|
|
103 |
return ret;
|
|
104 |
}
|
|
105 |
}
|
|
106 |
|
|
107 |
ret = bdrv_pwrite(bs->file, c->entries[i].offset, c->entries[i].table,
|
|
108 |
s->cluster_size);
|
|
109 |
if (ret < 0) {
|
|
110 |
return ret;
|
|
111 |
}
|
|
112 |
|
|
113 |
c->entries[i].dirty = false;
|
|
114 |
|
|
115 |
return 0;
|
|
116 |
}
|
|
117 |
|
|
118 |
int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c)
|
|
119 |
{
|
|
120 |
int result = 0;
|
|
121 |
int ret;
|
|
122 |
int i;
|
|
123 |
|
|
124 |
for (i = 0; i < c->size; i++) {
|
|
125 |
ret = qcow2_cache_entry_flush(bs, c, i);
|
|
126 |
if (ret < 0 && result != -ENOSPC) {
|
|
127 |
result = ret;
|
|
128 |
}
|
|
129 |
}
|
|
130 |
|
|
131 |
if (result == 0) {
|
|
132 |
ret = bdrv_flush(bs->file);
|
|
133 |
if (ret < 0) {
|
|
134 |
result = ret;
|
|
135 |
}
|
|
136 |
}
|
|
137 |
|
|
138 |
return result;
|
|
139 |
}
|
|
140 |
|
|
141 |
int qcow2_cache_set_dependency(BlockDriverState *bs, Qcow2Cache *c,
|
|
142 |
Qcow2Cache *dependency)
|
|
143 |
{
|
|
144 |
int ret;
|
|
145 |
|
|
146 |
if (dependency->depends) {
|
|
147 |
ret = qcow2_cache_flush_dependency(bs, dependency);
|
|
148 |
if (ret < 0) {
|
|
149 |
return ret;
|
|
150 |
}
|
|
151 |
}
|
|
152 |
|
|
153 |
if (c->depends && (c->depends != dependency)) {
|
|
154 |
ret = qcow2_cache_flush_dependency(bs, c);
|
|
155 |
if (ret < 0) {
|
|
156 |
return ret;
|
|
157 |
}
|
|
158 |
}
|
|
159 |
|
|
160 |
c->depends = dependency;
|
|
161 |
return 0;
|
|
162 |
}
|
|
163 |
|
|
164 |
static int qcow2_cache_find_entry_to_replace(Qcow2Cache *c)
|
|
165 |
{
|
|
166 |
int i;
|
|
167 |
int min_count = INT_MAX;
|
|
168 |
int min_index = -1;
|
|
169 |
|
|
170 |
|
|
171 |
for (i = 0; i < c->size; i++) {
|
|
172 |
if (c->entries[i].ref) {
|
|
173 |
continue;
|
|
174 |
}
|
|
175 |
|
|
176 |
if (c->entries[i].cache_hits < min_count) {
|
|
177 |
min_index = i;
|
|
178 |
min_count = c->entries[i].cache_hits;
|
|
179 |
}
|
|
180 |
|
|
181 |
/* Give newer hits priority */
|
|
182 |
/* TODO Check how to optimize the replacement strategy */
|
|
183 |
c->entries[i].cache_hits /= 2;
|
|
184 |
}
|
|
185 |
|
|
186 |
if (min_index == -1) {
|
|
187 |
/* This can't happen in current synchronous code, but leave the check
|
|
188 |
* here as a reminder for whoever starts using AIO with the cache */
|
|
189 |
abort();
|
|
190 |
}
|
|
191 |
return min_index;
|
|
192 |
}
|
|
193 |
|
|
194 |
static int qcow2_cache_do_get(BlockDriverState *bs, Qcow2Cache *c,
|
|
195 |
uint64_t offset, void **table, bool read_from_disk)
|
|
196 |
{
|
|
197 |
BDRVQcowState *s = bs->opaque;
|
|
198 |
int i;
|
|
199 |
int ret;
|
|
200 |
|
|
201 |
/* Check if the table is already cached */
|
|
202 |
for (i = 0; i < c->size; i++) {
|
|
203 |
if (c->entries[i].offset == offset) {
|
|
204 |
goto found;
|
|
205 |
}
|
|
206 |
}
|
|
207 |
|
|
208 |
/* If not, write a table back and replace it */
|
|
209 |
i = qcow2_cache_find_entry_to_replace(c);
|
|
210 |
if (i < 0) {
|
|
211 |
return i;
|
|
212 |
}
|
|
213 |
|
|
214 |
ret = qcow2_cache_entry_flush(bs, c, i);
|
|
215 |
if (ret < 0) {
|
|
216 |
return ret;
|
|
217 |
}
|
|
218 |
|
|
219 |
c->entries[i].offset = 0;
|
|
220 |
if (read_from_disk) {
|
|
221 |
ret = bdrv_pread(bs->file, offset, c->entries[i].table, s->cluster_size);
|
|
222 |
if (ret < 0) {
|
|
223 |
return ret;
|
|
224 |
}
|
|
225 |
}
|
|
226 |
|
|
227 |
/* Give the table some hits for the start so that it won't be replaced
|
|
228 |
* immediately. The number 32 is completely arbitrary. */
|
|
229 |
c->entries[i].cache_hits = 32;
|
|
230 |
c->entries[i].offset = offset;
|
|
231 |
|
|
232 |
/* And return the right table */
|
|
233 |
found:
|
|
234 |
c->entries[i].cache_hits++;
|
|
235 |
c->entries[i].ref++;
|
|
236 |
*table = c->entries[i].table;
|
|
237 |
return 0;
|
|
238 |
}
|
|
239 |
|
|
240 |
int qcow2_cache_get(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
|
|
241 |
void **table)
|
|
242 |
{
|
|
243 |
return qcow2_cache_do_get(bs, c, offset, table, true);
|
|
244 |
}
|
|
245 |
|
|
246 |
int qcow2_cache_get_empty(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
|
|
247 |
void **table)
|
|
248 |
{
|
|
249 |
return qcow2_cache_do_get(bs, c, offset, table, false);
|
|
250 |
}
|
|
251 |
|
|
252 |
int qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table)
|
|
253 |
{
|
|
254 |
int i;
|
|
255 |
|
|
256 |
for (i = 0; i < c->size; i++) {
|
|
257 |
if (c->entries[i].table == *table) {
|
|
258 |
goto found;
|
|
259 |
}
|
|
260 |
}
|
|
261 |
return -ENOENT;
|
|
262 |
|
|
263 |
found:
|
|
264 |
c->entries[i].ref--;
|
|
265 |
*table = NULL;
|
|
266 |
|
|
267 |
assert(c->entries[i].ref >= 0);
|
|
268 |
|
|
269 |
if (c->writethrough) {
|
|
270 |
return qcow2_cache_entry_flush(bs, c, i);
|
|
271 |
} else {
|
|
272 |
return 0;
|
|
273 |
}
|
|
274 |
}
|
|
275 |
|
|
276 |
void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table)
|
|
277 |
{
|
|
278 |
int i;
|
|
279 |
|
|
280 |
for (i = 0; i < c->size; i++) {
|
|
281 |
if (c->entries[i].table == table) {
|
|
282 |
goto found;
|
|
283 |
}
|
|
284 |
}
|
|
285 |
abort();
|
|
286 |
|
|
287 |
found:
|
|
288 |
c->entries[i].dirty = true;
|
|
289 |
}
|
|
290 |
|