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1 /*
2 * QEMU Enhanced Disk Format
3 *
4 * Copyright IBM, Corp. 2010
5 *
6 * Authors:
7 * Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
8 * Anthony Liguori <aliguori@us.ibm.com>
9 *
10 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
11 * See the COPYING.LIB file in the top-level directory.
12 *
13 */
14
15 #ifndef BLOCK_QED_H
16 #define BLOCK_QED_H
17
18 #include "block_int.h"
19
20 /* The layout of a QED file is as follows:
21 *
22 * +--------+----------+----------+----------+-----+
23 * | header | L1 table | cluster0 | cluster1 | ... |
24 * +--------+----------+----------+----------+-----+
25 *
26 * There is a 2-level pagetable for cluster allocation:
27 *
28 * +----------+
29 * | L1 table |
30 * +----------+
31 * ,------' | '------.
32 * +----------+ | +----------+
33 * | L2 table | ... | L2 table |
34 * +----------+ +----------+
35 * ,------' | '------.
36 * +----------+ | +----------+
37 * | Data | ... | Data |
38 * +----------+ +----------+
39 *
40 * The L1 table is fixed size and always present. L2 tables are allocated on
41 * demand. The L1 table size determines the maximum possible image size; it
42 * can be influenced using the cluster_size and table_size values.
43 *
44 * All fields are little-endian on disk.
45 */
46
47 enum {
48 QED_MAGIC = 'Q' | 'E' << 8 | 'D' << 16 | '\0' << 24,
49
50 /* The image supports a backing file */
51 QED_F_BACKING_FILE = 0x01,
52
53 /* The image needs a consistency check before use */
54 QED_F_NEED_CHECK = 0x02,
55
56 /* The backing file format must not be probed, treat as raw image */
57 QED_F_BACKING_FORMAT_NO_PROBE = 0x04,
58
59 /* Feature bits must be used when the on-disk format changes */
60 QED_FEATURE_MASK = QED_F_BACKING_FILE | /* supported feature bits */
61 QED_F_NEED_CHECK |
62 QED_F_BACKING_FORMAT_NO_PROBE,
63 QED_COMPAT_FEATURE_MASK = 0, /* supported compat feature bits */
64 QED_AUTOCLEAR_FEATURE_MASK = 0, /* supported autoclear feature bits */
65
66 /* Data is stored in groups of sectors called clusters. Cluster size must
67 * be large to avoid keeping too much metadata. I/O requests that have
68 * sub-cluster size will require read-modify-write.
69 */
70 QED_MIN_CLUSTER_SIZE = 4 * 1024, /* in bytes */
71 QED_MAX_CLUSTER_SIZE = 64 * 1024 * 1024,
72 QED_DEFAULT_CLUSTER_SIZE = 64 * 1024,
73
74 /* Allocated clusters are tracked using a 2-level pagetable. Table size is
75 * a multiple of clusters so large maximum image sizes can be supported
76 * without jacking up the cluster size too much.
77 */
78 QED_MIN_TABLE_SIZE = 1, /* in clusters */
79 QED_MAX_TABLE_SIZE = 16,
80 QED_DEFAULT_TABLE_SIZE = 4,
81
82 /* Delay to flush and clean image after last allocating write completes */
83 QED_NEED_CHECK_TIMEOUT = 5, /* in seconds */
84 };
85
86 typedef struct {
87 uint32_t magic; /* QED\0 */
88
89 uint32_t cluster_size; /* in bytes */
90 uint32_t table_size; /* for L1 and L2 tables, in clusters */
91 uint32_t header_size; /* in clusters */
92
93 uint64_t features; /* format feature bits */
94 uint64_t compat_features; /* compatible feature bits */
95 uint64_t autoclear_features; /* self-resetting feature bits */
96
97 uint64_t l1_table_offset; /* in bytes */
98 uint64_t image_size; /* total logical image size, in bytes */
99
100 /* if (features & QED_F_BACKING_FILE) */
101 uint32_t backing_filename_offset; /* in bytes from start of header */
102 uint32_t backing_filename_size; /* in bytes */
103 } QEDHeader;
104
105 typedef struct {
106 uint64_t offsets[0]; /* in bytes */
107 } QEDTable;
108
109 /* The L2 cache is a simple write-through cache for L2 structures */
110 typedef struct CachedL2Table {
111 QEDTable *table;
112 uint64_t offset; /* offset=0 indicates an invalidate entry */
113 QTAILQ_ENTRY(CachedL2Table) node;
114 int ref;
115 } CachedL2Table;
116
117 typedef struct {
118 QTAILQ_HEAD(, CachedL2Table) entries;
119 unsigned int n_entries;
120 } L2TableCache;
121
122 typedef struct QEDRequest {
123 CachedL2Table *l2_table;
124 } QEDRequest;
125
126 enum {
127 QED_AIOCB_WRITE = 0x0001, /* read or write? */
128 QED_AIOCB_ZERO = 0x0002, /* zero write, used with QED_AIOCB_WRITE */
129 };
130
131 typedef struct QEDAIOCB {
132 BlockDriverAIOCB common;
133 QEMUBH *bh;
134 int bh_ret; /* final return status for completion bh */
135 QSIMPLEQ_ENTRY(QEDAIOCB) next; /* next request */
136 int flags; /* QED_AIOCB_* bits ORed together */
137 bool *finished; /* signal for cancel completion */
138 uint64_t end_pos; /* request end on block device, in bytes */
139
140 /* User scatter-gather list */
141 QEMUIOVector *qiov;
142 size_t qiov_offset; /* byte count already processed */
143
144 /* Current cluster scatter-gather list */
145 QEMUIOVector cur_qiov;
146 uint64_t cur_pos; /* position on block device, in bytes */
147 uint64_t cur_cluster; /* cluster offset in image file */
148 unsigned int cur_nclusters; /* number of clusters being accessed */
149 int find_cluster_ret; /* used for L1/L2 update */
150
151 QEDRequest request;
152 } QEDAIOCB;
153
154 typedef struct {
155 BlockDriverState *bs; /* device */
156 uint64_t file_size; /* length of image file, in bytes */
157
158 QEDHeader header; /* always cpu-endian */
159 QEDTable *l1_table;
160 L2TableCache l2_cache; /* l2 table cache */
161 uint32_t table_nelems;
162 uint32_t l1_shift;
163 uint32_t l2_shift;
164 uint32_t l2_mask;
165
166 /* Allocating write request queue */
167 QSIMPLEQ_HEAD(, QEDAIOCB) allocating_write_reqs;
168 bool allocating_write_reqs_plugged;
169
170 /* Periodic flush and clear need check flag */
171 QEMUTimer *need_check_timer;
172
173 Error *migration_blocker;
174 } BDRVQEDState;
175
176 enum {
177 QED_CLUSTER_FOUND, /* cluster found */
178 QED_CLUSTER_ZERO, /* zero cluster found */
179 QED_CLUSTER_L2, /* cluster missing in L2 */
180 QED_CLUSTER_L1, /* cluster missing in L1 */
181 };
182
183 /**
184 * qed_find_cluster() completion callback
185 *
186 * @opaque: User data for completion callback
187 * @ret: QED_CLUSTER_FOUND Success
188 * QED_CLUSTER_L2 Data cluster unallocated in L2
189 * QED_CLUSTER_L1 L2 unallocated in L1
190 * -errno POSIX error occurred
191 * @offset: Data cluster offset
192 * @len: Contiguous bytes starting from cluster offset
193 *
194 * This function is invoked when qed_find_cluster() completes.
195 *
196 * On success ret is QED_CLUSTER_FOUND and offset/len are a contiguous range
197 * in the image file.
198 *
199 * On failure ret is QED_CLUSTER_L2 or QED_CLUSTER_L1 for missing L2 or L1
200 * table offset, respectively. len is number of contiguous unallocated bytes.
201 */
202 typedef void QEDFindClusterFunc(void *opaque, int ret, uint64_t offset, size_t len);
203
204 /**
205 * Generic callback for chaining async callbacks
206 */
207 typedef struct {
208 BlockDriverCompletionFunc *cb;
209 void *opaque;
210 } GenericCB;
211
212 void *gencb_alloc(size_t len, BlockDriverCompletionFunc *cb, void *opaque);
213 void gencb_complete(void *opaque, int ret);
214
215 /**
216 * L2 cache functions
217 */
218 void qed_init_l2_cache(L2TableCache *l2_cache);
219 void qed_free_l2_cache(L2TableCache *l2_cache);
220 CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);
221 void qed_unref_l2_cache_entry(CachedL2Table *entry);
222 CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);
223 void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);
224
225 /**
226 * Table I/O functions
227 */
228 int qed_read_l1_table_sync(BDRVQEDState *s);
229 void qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n,
230 BlockDriverCompletionFunc *cb, void *opaque);
231 int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,
232 unsigned int n);
233 int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
234 uint64_t offset);
235 void qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset,
236 BlockDriverCompletionFunc *cb, void *opaque);
237 void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request,
238 unsigned int index, unsigned int n, bool flush,
239 BlockDriverCompletionFunc *cb, void *opaque);
240 int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
241 unsigned int index, unsigned int n, bool flush);
242
243 /**
244 * Cluster functions
245 */
246 void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
247 size_t len, QEDFindClusterFunc *cb, void *opaque);
248
249 /**
250 * Consistency check
251 */
252 int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);
253
254 QEDTable *qed_alloc_table(BDRVQEDState *s);
255
256 /**
257 * Round down to the start of a cluster
258 */
259 static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset)
260 {
261 return offset & ~(uint64_t)(s->header.cluster_size - 1);
262 }
263
264 static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)
265 {
266 return offset & (s->header.cluster_size - 1);
267 }
268
269 static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes)
270 {
271 return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) /
272 (s->header.cluster_size - 1);
273 }
274
275 static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)
276 {
277 return pos >> s->l1_shift;
278 }
279
280 static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos)
281 {
282 return (pos >> s->l2_shift) & s->l2_mask;
283 }
284
285 /**
286 * Test if a cluster offset is valid
287 */
288 static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset)
289 {
290 uint64_t header_size = (uint64_t)s->header.header_size *
291 s->header.cluster_size;
292
293 if (offset & (s->header.cluster_size - 1)) {
294 return false;
295 }
296 return offset >= header_size && offset < s->file_size;
297 }
298
299 /**
300 * Test if a table offset is valid
301 */
302 static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset)
303 {
304 uint64_t end_offset = offset + (s->header.table_size - 1) *
305 s->header.cluster_size;
306
307 /* Overflow check */
308 if (end_offset <= offset) {
309 return false;
310 }
311
312 return qed_check_cluster_offset(s, offset) &&
313 qed_check_cluster_offset(s, end_offset);
314 }
315
316 static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s,
317 uint64_t offset)
318 {
319 if (qed_offset_into_cluster(s, offset)) {
320 return false;
321 }
322 return true;
323 }
324
325 static inline bool qed_offset_is_unalloc_cluster(uint64_t offset)
326 {
327 if (offset == 0) {
328 return true;
329 }
330 return false;
331 }
332
333 static inline bool qed_offset_is_zero_cluster(uint64_t offset)
334 {
335 if (offset == 1) {
336 return true;
337 }
338 return false;
339 }
340
341 #endif /* BLOCK_QED_H */