qed: Periodically flush and clear need check bit
[qemu.git] / block / qed.h
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 typedef struct QEDAIOCB {
127 BlockDriverAIOCB common;
128 QEMUBH *bh;
129 int bh_ret; /* final return status for completion bh */
130 QSIMPLEQ_ENTRY(QEDAIOCB) next; /* next request */
131 bool is_write; /* false - read, true - write */
132 bool *finished; /* signal for cancel completion */
133 uint64_t end_pos; /* request end on block device, in bytes */
134
135 /* User scatter-gather list */
136 QEMUIOVector *qiov;
137 size_t qiov_offset; /* byte count already processed */
138
139 /* Current cluster scatter-gather list */
140 QEMUIOVector cur_qiov;
141 uint64_t cur_pos; /* position on block device, in bytes */
142 uint64_t cur_cluster; /* cluster offset in image file */
143 unsigned int cur_nclusters; /* number of clusters being accessed */
144 int find_cluster_ret; /* used for L1/L2 update */
145
146 QEDRequest request;
147 } QEDAIOCB;
148
149 typedef struct {
150 BlockDriverState *bs; /* device */
151 uint64_t file_size; /* length of image file, in bytes */
152
153 QEDHeader header; /* always cpu-endian */
154 QEDTable *l1_table;
155 L2TableCache l2_cache; /* l2 table cache */
156 uint32_t table_nelems;
157 uint32_t l1_shift;
158 uint32_t l2_shift;
159 uint32_t l2_mask;
160
161 /* Allocating write request queue */
162 QSIMPLEQ_HEAD(, QEDAIOCB) allocating_write_reqs;
163 bool allocating_write_reqs_plugged;
164
165 /* Periodic flush and clear need check flag */
166 QEMUTimer *need_check_timer;
167 } BDRVQEDState;
168
169 enum {
170 QED_CLUSTER_FOUND, /* cluster found */
171 QED_CLUSTER_ZERO, /* zero cluster found */
172 QED_CLUSTER_L2, /* cluster missing in L2 */
173 QED_CLUSTER_L1, /* cluster missing in L1 */
174 };
175
176 /**
177 * qed_find_cluster() completion callback
178 *
179 * @opaque: User data for completion callback
180 * @ret: QED_CLUSTER_FOUND Success
181 * QED_CLUSTER_L2 Data cluster unallocated in L2
182 * QED_CLUSTER_L1 L2 unallocated in L1
183 * -errno POSIX error occurred
184 * @offset: Data cluster offset
185 * @len: Contiguous bytes starting from cluster offset
186 *
187 * This function is invoked when qed_find_cluster() completes.
188 *
189 * On success ret is QED_CLUSTER_FOUND and offset/len are a contiguous range
190 * in the image file.
191 *
192 * On failure ret is QED_CLUSTER_L2 or QED_CLUSTER_L1 for missing L2 or L1
193 * table offset, respectively. len is number of contiguous unallocated bytes.
194 */
195 typedef void QEDFindClusterFunc(void *opaque, int ret, uint64_t offset, size_t len);
196
197 /**
198 * Generic callback for chaining async callbacks
199 */
200 typedef struct {
201 BlockDriverCompletionFunc *cb;
202 void *opaque;
203 } GenericCB;
204
205 void *gencb_alloc(size_t len, BlockDriverCompletionFunc *cb, void *opaque);
206 void gencb_complete(void *opaque, int ret);
207
208 /**
209 * L2 cache functions
210 */
211 void qed_init_l2_cache(L2TableCache *l2_cache);
212 void qed_free_l2_cache(L2TableCache *l2_cache);
213 CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);
214 void qed_unref_l2_cache_entry(CachedL2Table *entry);
215 CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);
216 void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);
217
218 /**
219 * Table I/O functions
220 */
221 int qed_read_l1_table_sync(BDRVQEDState *s);
222 void qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n,
223 BlockDriverCompletionFunc *cb, void *opaque);
224 int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,
225 unsigned int n);
226 int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
227 uint64_t offset);
228 void qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset,
229 BlockDriverCompletionFunc *cb, void *opaque);
230 void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request,
231 unsigned int index, unsigned int n, bool flush,
232 BlockDriverCompletionFunc *cb, void *opaque);
233 int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
234 unsigned int index, unsigned int n, bool flush);
235
236 /**
237 * Cluster functions
238 */
239 void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
240 size_t len, QEDFindClusterFunc *cb, void *opaque);
241
242 /**
243 * Consistency check
244 */
245 int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);
246
247 QEDTable *qed_alloc_table(BDRVQEDState *s);
248
249 /**
250 * Round down to the start of a cluster
251 */
252 static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset)
253 {
254 return offset & ~(uint64_t)(s->header.cluster_size - 1);
255 }
256
257 static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)
258 {
259 return offset & (s->header.cluster_size - 1);
260 }
261
262 static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes)
263 {
264 return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) /
265 (s->header.cluster_size - 1);
266 }
267
268 static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)
269 {
270 return pos >> s->l1_shift;
271 }
272
273 static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos)
274 {
275 return (pos >> s->l2_shift) & s->l2_mask;
276 }
277
278 /**
279 * Test if a cluster offset is valid
280 */
281 static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset)
282 {
283 uint64_t header_size = (uint64_t)s->header.header_size *
284 s->header.cluster_size;
285
286 if (offset & (s->header.cluster_size - 1)) {
287 return false;
288 }
289 return offset >= header_size && offset < s->file_size;
290 }
291
292 /**
293 * Test if a table offset is valid
294 */
295 static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset)
296 {
297 uint64_t end_offset = offset + (s->header.table_size - 1) *
298 s->header.cluster_size;
299
300 /* Overflow check */
301 if (end_offset <= offset) {
302 return false;
303 }
304
305 return qed_check_cluster_offset(s, offset) &&
306 qed_check_cluster_offset(s, end_offset);
307 }
308
309 static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s,
310 uint64_t offset)
311 {
312 if (qed_offset_into_cluster(s, offset)) {
313 return false;
314 }
315 return true;
316 }
317
318 static inline bool qed_offset_is_unalloc_cluster(uint64_t offset)
319 {
320 if (offset == 0) {
321 return true;
322 }
323 return false;
324 }
325
326 static inline bool qed_offset_is_zero_cluster(uint64_t offset)
327 {
328 if (offset == 1) {
329 return true;
330 }
331 return false;
332 }
333
334 #endif /* BLOCK_QED_H */