linux-user: Use safe_syscall for open and openat system calls
[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/block_int.h"
19 #include "qemu/cutils.h"
20
21 /* The layout of a QED file is as follows:
22 *
23 * +--------+----------+----------+----------+-----+
24 * | header | L1 table | cluster0 | cluster1 | ... |
25 * +--------+----------+----------+----------+-----+
26 *
27 * There is a 2-level pagetable for cluster allocation:
28 *
29 * +----------+
30 * | L1 table |
31 * +----------+
32 * ,------' | '------.
33 * +----------+ | +----------+
34 * | L2 table | ... | L2 table |
35 * +----------+ +----------+
36 * ,------' | '------.
37 * +----------+ | +----------+
38 * | Data | ... | Data |
39 * +----------+ +----------+
40 *
41 * The L1 table is fixed size and always present. L2 tables are allocated on
42 * demand. The L1 table size determines the maximum possible image size; it
43 * can be influenced using the cluster_size and table_size values.
44 *
45 * All fields are little-endian on disk.
46 */
47 #define QED_DEFAULT_CLUSTER_SIZE 65536
48 enum {
49 QED_MAGIC = 'Q' | 'E' << 8 | 'D' << 16 | '\0' << 24,
50
51 /* The image supports a backing file */
52 QED_F_BACKING_FILE = 0x01,
53
54 /* The image needs a consistency check before use */
55 QED_F_NEED_CHECK = 0x02,
56
57 /* The backing file format must not be probed, treat as raw image */
58 QED_F_BACKING_FORMAT_NO_PROBE = 0x04,
59
60 /* Feature bits must be used when the on-disk format changes */
61 QED_FEATURE_MASK = QED_F_BACKING_FILE | /* supported feature bits */
62 QED_F_NEED_CHECK |
63 QED_F_BACKING_FORMAT_NO_PROBE,
64 QED_COMPAT_FEATURE_MASK = 0, /* supported compat feature bits */
65 QED_AUTOCLEAR_FEATURE_MASK = 0, /* supported autoclear feature bits */
66
67 /* Data is stored in groups of sectors called clusters. Cluster size must
68 * be large to avoid keeping too much metadata. I/O requests that have
69 * sub-cluster size will require read-modify-write.
70 */
71 QED_MIN_CLUSTER_SIZE = 4 * 1024, /* in bytes */
72 QED_MAX_CLUSTER_SIZE = 64 * 1024 * 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 } QEMU_PACKED 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 BlockAIOCB 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 uint64_t end_pos; /* request end on block device, in bytes */
138
139 /* User scatter-gather list */
140 QEMUIOVector *qiov;
141 size_t qiov_offset; /* byte count already processed */
142
143 /* Current cluster scatter-gather list */
144 QEMUIOVector cur_qiov;
145 QEMUIOVector *backing_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 } BDRVQEDState;
173
174 enum {
175 QED_CLUSTER_FOUND, /* cluster found */
176 QED_CLUSTER_ZERO, /* zero cluster found */
177 QED_CLUSTER_L2, /* cluster missing in L2 */
178 QED_CLUSTER_L1, /* cluster missing in L1 */
179 };
180
181 /**
182 * qed_find_cluster() completion callback
183 *
184 * @opaque: User data for completion callback
185 * @ret: QED_CLUSTER_FOUND Success
186 * QED_CLUSTER_L2 Data cluster unallocated in L2
187 * QED_CLUSTER_L1 L2 unallocated in L1
188 * -errno POSIX error occurred
189 * @offset: Data cluster offset
190 * @len: Contiguous bytes starting from cluster offset
191 *
192 * This function is invoked when qed_find_cluster() completes.
193 *
194 * On success ret is QED_CLUSTER_FOUND and offset/len are a contiguous range
195 * in the image file.
196 *
197 * On failure ret is QED_CLUSTER_L2 or QED_CLUSTER_L1 for missing L2 or L1
198 * table offset, respectively. len is number of contiguous unallocated bytes.
199 */
200 typedef void QEDFindClusterFunc(void *opaque, int ret, uint64_t offset, size_t len);
201
202 /**
203 * Generic callback for chaining async callbacks
204 */
205 typedef struct {
206 BlockCompletionFunc *cb;
207 void *opaque;
208 } GenericCB;
209
210 void *gencb_alloc(size_t len, BlockCompletionFunc *cb, void *opaque);
211 void gencb_complete(void *opaque, int ret);
212
213 /**
214 * Header functions
215 */
216 int qed_write_header_sync(BDRVQEDState *s);
217
218 /**
219 * L2 cache functions
220 */
221 void qed_init_l2_cache(L2TableCache *l2_cache);
222 void qed_free_l2_cache(L2TableCache *l2_cache);
223 CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);
224 void qed_unref_l2_cache_entry(CachedL2Table *entry);
225 CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);
226 void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);
227
228 /**
229 * Table I/O functions
230 */
231 int qed_read_l1_table_sync(BDRVQEDState *s);
232 void qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n,
233 BlockCompletionFunc *cb, void *opaque);
234 int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,
235 unsigned int n);
236 int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
237 uint64_t offset);
238 void qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset,
239 BlockCompletionFunc *cb, void *opaque);
240 void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request,
241 unsigned int index, unsigned int n, bool flush,
242 BlockCompletionFunc *cb, void *opaque);
243 int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
244 unsigned int index, unsigned int n, bool flush);
245
246 /**
247 * Cluster functions
248 */
249 void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
250 size_t len, QEDFindClusterFunc *cb, void *opaque);
251
252 /**
253 * Consistency check
254 */
255 int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);
256
257 QEDTable *qed_alloc_table(BDRVQEDState *s);
258
259 /**
260 * Round down to the start of a cluster
261 */
262 static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset)
263 {
264 return offset & ~(uint64_t)(s->header.cluster_size - 1);
265 }
266
267 static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)
268 {
269 return offset & (s->header.cluster_size - 1);
270 }
271
272 static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes)
273 {
274 return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) /
275 (s->header.cluster_size - 1);
276 }
277
278 static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)
279 {
280 return pos >> s->l1_shift;
281 }
282
283 static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos)
284 {
285 return (pos >> s->l2_shift) & s->l2_mask;
286 }
287
288 /**
289 * Test if a cluster offset is valid
290 */
291 static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset)
292 {
293 uint64_t header_size = (uint64_t)s->header.header_size *
294 s->header.cluster_size;
295
296 if (offset & (s->header.cluster_size - 1)) {
297 return false;
298 }
299 return offset >= header_size && offset < s->file_size;
300 }
301
302 /**
303 * Test if a table offset is valid
304 */
305 static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset)
306 {
307 uint64_t end_offset = offset + (s->header.table_size - 1) *
308 s->header.cluster_size;
309
310 /* Overflow check */
311 if (end_offset <= offset) {
312 return false;
313 }
314
315 return qed_check_cluster_offset(s, offset) &&
316 qed_check_cluster_offset(s, end_offset);
317 }
318
319 static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s,
320 uint64_t offset)
321 {
322 if (qed_offset_into_cluster(s, offset)) {
323 return false;
324 }
325 return true;
326 }
327
328 static inline bool qed_offset_is_unalloc_cluster(uint64_t offset)
329 {
330 if (offset == 0) {
331 return true;
332 }
333 return false;
334 }
335
336 static inline bool qed_offset_is_zero_cluster(uint64_t offset)
337 {
338 if (offset == 1) {
339 return true;
340 }
341 return false;
342 }
343
344 #endif /* BLOCK_QED_H */