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
  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 */