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 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 } 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 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 } 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 BlockDriverCompletionFunc *cb; 207 void *opaque; 208 } GenericCB; 209 210 void *gencb_alloc(size_t len, BlockDriverCompletionFunc *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 BlockDriverCompletionFunc *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 BlockDriverCompletionFunc *cb, void *opaque); 240 void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request, 241 unsigned int index, unsigned int n, bool flush, 242 BlockDriverCompletionFunc *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 */ 345