LXR qemu/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_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
  47enum {
  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
  86typedef 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} QEDHeader;
 104
 105typedef struct {
 106    uint64_t offsets[0];            /* in bytes */
 107} QEDTable;
 108
 109/* The L2 cache is a simple write-through cache for L2 structures */
 110typedef 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
 117typedef struct {
 118    QTAILQ_HEAD(, CachedL2Table) entries;
 119    unsigned int n_entries;
 120} L2TableCache;
 121
 122typedef struct QEDRequest {
 123    CachedL2Table *l2_table;
 124} QEDRequest;
 125
 126enum {
 127    QED_AIOCB_WRITE = 0x0001,       /* read or write? */
 128    QED_AIOCB_ZERO  = 0x0002,       /* zero write, used with QED_AIOCB_WRITE */
 129};
 130
 131typedef 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
 154typedef 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
 174enum {
 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 */
 200typedef void QEDFindClusterFunc(void *opaque, int ret, uint64_t offset, size_t len);
 201
 202/**
 203 * Generic callback for chaining async callbacks
 204 */
 205typedef struct {
 206    BlockDriverCompletionFunc *cb;
 207    void *opaque;
 208} GenericCB;
 209
 210void *gencb_alloc(size_t len, BlockDriverCompletionFunc *cb, void *opaque);
 211void gencb_complete(void *opaque, int ret);
 212
 213/**
 214 * Header functions
 215 */
 216int qed_write_header_sync(BDRVQEDState *s);
 217
 218/**
 219 * L2 cache functions
 220 */
 221void qed_init_l2_cache(L2TableCache *l2_cache);
 222void qed_free_l2_cache(L2TableCache *l2_cache);
 223CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);
 224void qed_unref_l2_cache_entry(CachedL2Table *entry);
 225CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);
 226void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);
 227
 228/**
 229 * Table I/O functions
 230 */
 231int qed_read_l1_table_sync(BDRVQEDState *s);
 232void qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n,
 233                        BlockDriverCompletionFunc *cb, void *opaque);
 234int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,
 235                            unsigned int n);
 236int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
 237                           uint64_t offset);
 238void qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset,
 239                       BlockDriverCompletionFunc *cb, void *opaque);
 240void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request,
 241                        unsigned int index, unsigned int n, bool flush,
 242                        BlockDriverCompletionFunc *cb, void *opaque);
 243int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
 244                            unsigned int index, unsigned int n, bool flush);
 245
 246/**
 247 * Cluster functions
 248 */
 249void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
 250                      size_t len, QEDFindClusterFunc *cb, void *opaque);
 251
 252/**
 253 * Consistency check
 254 */
 255int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);
 256
 257QEDTable *qed_alloc_table(BDRVQEDState *s);
 258
 259/**
 260 * Round down to the start of a cluster
 261 */
 262static 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
 267static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)
 268{
 269    return offset & (s->header.cluster_size - 1);
 270}
 271
 272static 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
 278static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)
 279{
 280    return pos >> s->l1_shift;
 281}
 282
 283static 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 */
 291static 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 */
 305static 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
 319static 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
 328static inline bool qed_offset_is_unalloc_cluster(uint64_t offset)
 329{
 330    if (offset == 0) {
 331        return true;
 332    }
 333    return false;
 334}
 335
 336static 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