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 BlockDriverState *bs; 133 QSIMPLEQ_ENTRY(QEDAIOCB) next; /* next request */ 134 int flags; /* QED_AIOCB_* bits ORed together */ 135 uint64_t end_pos; /* request end on block device, in bytes */ 136 137 /* User scatter-gather list */ 138 QEMUIOVector *qiov; 139 size_t qiov_offset; /* byte count already processed */ 140 141 /* Current cluster scatter-gather list */ 142 QEMUIOVector cur_qiov; 143 QEMUIOVector *backing_qiov; 144 uint64_t cur_pos; /* position on block device, in bytes */ 145 uint64_t cur_cluster; /* cluster offset in image file */ 146 unsigned int cur_nclusters; /* number of clusters being accessed */ 147 int find_cluster_ret; /* used for L1/L2 update */ 148 149 QEDRequest request; 150 } QEDAIOCB; 151 152 typedef struct { 153 BlockDriverState *bs; /* device */ 154 155 /* Written only by an allocating write or the timer handler (the latter 156 * while allocating reqs are plugged). 157 */ 158 QEDHeader header; /* always cpu-endian */ 159 160 /* Protected by table_lock. */ 161 CoMutex table_lock; 162 QEDTable *l1_table; 163 L2TableCache l2_cache; /* l2 table cache */ 164 uint32_t table_nelems; 165 uint32_t l1_shift; 166 uint32_t l2_shift; 167 uint32_t l2_mask; 168 uint64_t file_size; /* length of image file, in bytes */ 169 170 /* Allocating write request queue */ 171 QEDAIOCB *allocating_acb; 172 CoQueue allocating_write_reqs; 173 bool allocating_write_reqs_plugged; 174 175 /* Periodic flush and clear need check flag */ 176 QEMUTimer *need_check_timer; 177 } BDRVQEDState; 178 179 enum { 180 QED_CLUSTER_FOUND, /* cluster found */ 181 QED_CLUSTER_ZERO, /* zero cluster found */ 182 QED_CLUSTER_L2, /* cluster missing in L2 */ 183 QED_CLUSTER_L1, /* cluster missing in L1 */ 184 }; 185 186 /** 187 * Header functions 188 */ 189 int qed_write_header_sync(BDRVQEDState *s); 190 191 /** 192 * L2 cache functions 193 */ 194 void qed_init_l2_cache(L2TableCache *l2_cache); 195 void qed_free_l2_cache(L2TableCache *l2_cache); 196 CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache); 197 void qed_unref_l2_cache_entry(CachedL2Table *entry); 198 CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset); 199 void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table); 200 201 /** 202 * Table I/O functions 203 */ 204 int coroutine_fn qed_read_l1_table_sync(BDRVQEDState *s); 205 int coroutine_fn qed_write_l1_table(BDRVQEDState *s, unsigned int index, 206 unsigned int n); 207 int coroutine_fn qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index, 208 unsigned int n); 209 int coroutine_fn qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request, 210 uint64_t offset); 211 int coroutine_fn qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, 212 uint64_t offset); 213 int coroutine_fn qed_write_l2_table(BDRVQEDState *s, QEDRequest *request, 214 unsigned int index, unsigned int n, 215 bool flush); 216 int coroutine_fn qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request, 217 unsigned int index, unsigned int n, 218 bool flush); 219 220 /** 221 * Cluster functions 222 */ 223 int coroutine_fn qed_find_cluster(BDRVQEDState *s, QEDRequest *request, 224 uint64_t pos, size_t *len, 225 uint64_t *img_offset); 226 227 /** 228 * Consistency check 229 */ 230 int coroutine_fn qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix); 231 232 QEDTable *qed_alloc_table(BDRVQEDState *s); 233 234 /** 235 * Round down to the start of a cluster 236 */ 237 static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset) 238 { 239 return offset & ~(uint64_t)(s->header.cluster_size - 1); 240 } 241 242 static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset) 243 { 244 return offset & (s->header.cluster_size - 1); 245 } 246 247 static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes) 248 { 249 return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) / 250 (s->header.cluster_size - 1); 251 } 252 253 static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos) 254 { 255 return pos >> s->l1_shift; 256 } 257 258 static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos) 259 { 260 return (pos >> s->l2_shift) & s->l2_mask; 261 } 262 263 /** 264 * Test if a cluster offset is valid 265 */ 266 static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset) 267 { 268 uint64_t header_size = (uint64_t)s->header.header_size * 269 s->header.cluster_size; 270 271 if (offset & (s->header.cluster_size - 1)) { 272 return false; 273 } 274 return offset >= header_size && offset < s->file_size; 275 } 276 277 /** 278 * Test if a table offset is valid 279 */ 280 static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset) 281 { 282 uint64_t end_offset = offset + (s->header.table_size - 1) * 283 s->header.cluster_size; 284 285 /* Overflow check */ 286 if (end_offset <= offset) { 287 return false; 288 } 289 290 return qed_check_cluster_offset(s, offset) && 291 qed_check_cluster_offset(s, end_offset); 292 } 293 294 static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s, 295 uint64_t offset) 296 { 297 if (qed_offset_into_cluster(s, offset)) { 298 return false; 299 } 300 return true; 301 } 302 303 static inline bool qed_offset_is_unalloc_cluster(uint64_t offset) 304 { 305 if (offset == 0) { 306 return true; 307 } 308 return false; 309 } 310 311 static inline bool qed_offset_is_zero_cluster(uint64_t offset) 312 { 313 if (offset == 1) { 314 return true; 315 } 316 return false; 317 } 318 319 #endif /* BLOCK_QED_H */ 320