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 qed_read_l1_table_sync(BDRVQEDState *s); 205 int qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n); 206 int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index, 207 unsigned int n); 208 int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request, 209 uint64_t offset); 210 int qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset); 211 int qed_write_l2_table(BDRVQEDState *s, QEDRequest *request, 212 unsigned int index, unsigned int n, bool flush); 213 int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request, 214 unsigned int index, unsigned int n, bool flush); 215 216 /** 217 * Cluster functions 218 */ 219 int coroutine_fn qed_find_cluster(BDRVQEDState *s, QEDRequest *request, 220 uint64_t pos, size_t *len, 221 uint64_t *img_offset); 222 223 /** 224 * Consistency check 225 */ 226 int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix); 227 228 QEDTable *qed_alloc_table(BDRVQEDState *s); 229 230 /** 231 * Round down to the start of a cluster 232 */ 233 static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset) 234 { 235 return offset & ~(uint64_t)(s->header.cluster_size - 1); 236 } 237 238 static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset) 239 { 240 return offset & (s->header.cluster_size - 1); 241 } 242 243 static inline uint64_t qed_bytes_to_clusters(BDRVQEDState *s, uint64_t bytes) 244 { 245 return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) / 246 (s->header.cluster_size - 1); 247 } 248 249 static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos) 250 { 251 return pos >> s->l1_shift; 252 } 253 254 static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos) 255 { 256 return (pos >> s->l2_shift) & s->l2_mask; 257 } 258 259 /** 260 * Test if a cluster offset is valid 261 */ 262 static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset) 263 { 264 uint64_t header_size = (uint64_t)s->header.header_size * 265 s->header.cluster_size; 266 267 if (offset & (s->header.cluster_size - 1)) { 268 return false; 269 } 270 return offset >= header_size && offset < s->file_size; 271 } 272 273 /** 274 * Test if a table offset is valid 275 */ 276 static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset) 277 { 278 uint64_t end_offset = offset + (s->header.table_size - 1) * 279 s->header.cluster_size; 280 281 /* Overflow check */ 282 if (end_offset <= offset) { 283 return false; 284 } 285 286 return qed_check_cluster_offset(s, offset) && 287 qed_check_cluster_offset(s, end_offset); 288 } 289 290 static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s, 291 uint64_t offset) 292 { 293 if (qed_offset_into_cluster(s, offset)) { 294 return false; 295 } 296 return true; 297 } 298 299 static inline bool qed_offset_is_unalloc_cluster(uint64_t offset) 300 { 301 if (offset == 0) { 302 return true; 303 } 304 return false; 305 } 306 307 static inline bool qed_offset_is_zero_cluster(uint64_t offset) 308 { 309 if (offset == 1) { 310 return true; 311 } 312 return false; 313 } 314 315 #endif /* BLOCK_QED_H */ 316