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 #define QED_DEFAULT_CLUSTER_SIZE 65536 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 73 /* Allocated clusters are tracked using a 2-level pagetable. Table size is 74 * a multiple of clusters so large maximum image sizes can be supported 75 * without jacking up the cluster size too much. 76 */ 77 QED_MIN_TABLE_SIZE = 1, /* in clusters */ 78 QED_MAX_TABLE_SIZE = 16, 79 QED_DEFAULT_TABLE_SIZE = 4, 80 81 /* Delay to flush and clean image after last allocating write completes */ 82 QED_NEED_CHECK_TIMEOUT = 5, /* in seconds */ 83 }; 84 85 typedef struct { 86 uint32_t magic; /* QED\0 */ 87 88 uint32_t cluster_size; /* in bytes */ 89 uint32_t table_size; /* for L1 and L2 tables, in clusters */ 90 uint32_t header_size; /* in clusters */ 91 92 uint64_t features; /* format feature bits */ 93 uint64_t compat_features; /* compatible feature bits */ 94 uint64_t autoclear_features; /* self-resetting feature bits */ 95 96 uint64_t l1_table_offset; /* in bytes */ 97 uint64_t image_size; /* total logical image size, in bytes */ 98 99 /* if (features & QED_F_BACKING_FILE) */ 100 uint32_t backing_filename_offset; /* in bytes from start of header */ 101 uint32_t backing_filename_size; /* in bytes */ 102 } QEMU_PACKED QEDHeader; 103 104 typedef struct { 105 uint64_t offsets[0]; /* in bytes */ 106 } QEDTable; 107 108 /* The L2 cache is a simple write-through cache for L2 structures */ 109 typedef struct CachedL2Table { 110 QEDTable *table; 111 uint64_t offset; /* offset=0 indicates an invalidate entry */ 112 QTAILQ_ENTRY(CachedL2Table) node; 113 int ref; 114 } CachedL2Table; 115 116 typedef struct { 117 QTAILQ_HEAD(, CachedL2Table) entries; 118 unsigned int n_entries; 119 } L2TableCache; 120 121 typedef struct QEDRequest { 122 CachedL2Table *l2_table; 123 } QEDRequest; 124 125 enum { 126 QED_AIOCB_WRITE = 0x0001, /* read or write? */ 127 QED_AIOCB_ZERO = 0x0002, /* zero write, used with QED_AIOCB_WRITE */ 128 }; 129 130 typedef struct QEDAIOCB { 131 BlockAIOCB common; 132 QEMUBH *bh; 133 int bh_ret; /* final return status for completion bh */ 134 QSIMPLEQ_ENTRY(QEDAIOCB) next; /* next request */ 135 int flags; /* QED_AIOCB_* bits ORed together */ 136 uint64_t end_pos; /* request end on block device, in bytes */ 137 138 /* User scatter-gather list */ 139 QEMUIOVector *qiov; 140 size_t qiov_offset; /* byte count already processed */ 141 142 /* Current cluster scatter-gather list */ 143 QEMUIOVector cur_qiov; 144 QEMUIOVector *backing_qiov; 145 uint64_t cur_pos; /* position on block device, in bytes */ 146 uint64_t cur_cluster; /* cluster offset in image file */ 147 unsigned int cur_nclusters; /* number of clusters being accessed */ 148 int find_cluster_ret; /* used for L1/L2 update */ 149 150 QEDRequest request; 151 } QEDAIOCB; 152 153 typedef struct { 154 BlockDriverState *bs; /* device */ 155 uint64_t file_size; /* length of image file, in bytes */ 156 157 QEDHeader header; /* always cpu-endian */ 158 QEDTable *l1_table; 159 L2TableCache l2_cache; /* l2 table cache */ 160 uint32_t table_nelems; 161 uint32_t l1_shift; 162 uint32_t l2_shift; 163 uint32_t l2_mask; 164 165 /* Allocating write request queue */ 166 QSIMPLEQ_HEAD(, QEDAIOCB) allocating_write_reqs; 167 bool allocating_write_reqs_plugged; 168 169 /* Periodic flush and clear need check flag */ 170 QEMUTimer *need_check_timer; 171 } BDRVQEDState; 172 173 enum { 174 QED_CLUSTER_FOUND, /* cluster found */ 175 QED_CLUSTER_ZERO, /* zero cluster found */ 176 QED_CLUSTER_L2, /* cluster missing in L2 */ 177 QED_CLUSTER_L1, /* cluster missing in L1 */ 178 }; 179 180 /** 181 * qed_find_cluster() completion callback 182 * 183 * @opaque: User data for completion callback 184 * @ret: QED_CLUSTER_FOUND Success 185 * QED_CLUSTER_L2 Data cluster unallocated in L2 186 * QED_CLUSTER_L1 L2 unallocated in L1 187 * -errno POSIX error occurred 188 * @offset: Data cluster offset 189 * @len: Contiguous bytes starting from cluster offset 190 * 191 * This function is invoked when qed_find_cluster() completes. 192 * 193 * On success ret is QED_CLUSTER_FOUND and offset/len are a contiguous range 194 * in the image file. 195 * 196 * On failure ret is QED_CLUSTER_L2 or QED_CLUSTER_L1 for missing L2 or L1 197 * table offset, respectively. len is number of contiguous unallocated bytes. 198 */ 199 typedef void QEDFindClusterFunc(void *opaque, int ret, uint64_t offset, size_t len); 200 201 /** 202 * Generic callback for chaining async callbacks 203 */ 204 typedef struct { 205 BlockCompletionFunc *cb; 206 void *opaque; 207 } GenericCB; 208 209 void *gencb_alloc(size_t len, BlockCompletionFunc *cb, void *opaque); 210 void gencb_complete(void *opaque, int ret); 211 212 /** 213 * Header functions 214 */ 215 int qed_write_header_sync(BDRVQEDState *s); 216 217 /** 218 * L2 cache functions 219 */ 220 void qed_init_l2_cache(L2TableCache *l2_cache); 221 void qed_free_l2_cache(L2TableCache *l2_cache); 222 CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache); 223 void qed_unref_l2_cache_entry(CachedL2Table *entry); 224 CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset); 225 void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table); 226 227 /** 228 * Table I/O functions 229 */ 230 int qed_read_l1_table_sync(BDRVQEDState *s); 231 void qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n, 232 BlockCompletionFunc *cb, void *opaque); 233 int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index, 234 unsigned int n); 235 int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request, 236 uint64_t offset); 237 void qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset, 238 BlockCompletionFunc *cb, void *opaque); 239 void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request, 240 unsigned int index, unsigned int n, bool flush, 241 BlockCompletionFunc *cb, void *opaque); 242 int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request, 243 unsigned int index, unsigned int n, bool flush); 244 245 /** 246 * Cluster functions 247 */ 248 void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos, 249 size_t len, QEDFindClusterFunc *cb, void *opaque); 250 251 /** 252 * Consistency check 253 */ 254 int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix); 255 256 QEDTable *qed_alloc_table(BDRVQEDState *s); 257 258 /** 259 * Round down to the start of a cluster 260 */ 261 static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset) 262 { 263 return offset & ~(uint64_t)(s->header.cluster_size - 1); 264 } 265 266 static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset) 267 { 268 return offset & (s->header.cluster_size - 1); 269 } 270 271 static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes) 272 { 273 return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) / 274 (s->header.cluster_size - 1); 275 } 276 277 static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos) 278 { 279 return pos >> s->l1_shift; 280 } 281 282 static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos) 283 { 284 return (pos >> s->l2_shift) & s->l2_mask; 285 } 286 287 /** 288 * Test if a cluster offset is valid 289 */ 290 static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset) 291 { 292 uint64_t header_size = (uint64_t)s->header.header_size * 293 s->header.cluster_size; 294 295 if (offset & (s->header.cluster_size - 1)) { 296 return false; 297 } 298 return offset >= header_size && offset < s->file_size; 299 } 300 301 /** 302 * Test if a table offset is valid 303 */ 304 static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset) 305 { 306 uint64_t end_offset = offset + (s->header.table_size - 1) * 307 s->header.cluster_size; 308 309 /* Overflow check */ 310 if (end_offset <= offset) { 311 return false; 312 } 313 314 return qed_check_cluster_offset(s, offset) && 315 qed_check_cluster_offset(s, end_offset); 316 } 317 318 static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s, 319 uint64_t offset) 320 { 321 if (qed_offset_into_cluster(s, offset)) { 322 return false; 323 } 324 return true; 325 } 326 327 static inline bool qed_offset_is_unalloc_cluster(uint64_t offset) 328 { 329 if (offset == 0) { 330 return true; 331 } 332 return false; 333 } 334 335 static inline bool qed_offset_is_zero_cluster(uint64_t offset) 336 { 337 if (offset == 1) { 338 return true; 339 } 340 return false; 341 } 342 343 #endif /* BLOCK_QED_H */ 344