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/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
  48enum {
  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
  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} QEMU_PACKED 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    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
 152typedef 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
 179enum {
 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 */
 189int qed_write_header_sync(BDRVQEDState *s);
 190
 191/**
 192 * L2 cache functions
 193 */
 194void qed_init_l2_cache(L2TableCache *l2_cache);
 195void qed_free_l2_cache(L2TableCache *l2_cache);
 196CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);
 197void qed_unref_l2_cache_entry(CachedL2Table *entry);
 198CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);
 199void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);
 200
 201/**
 202 * Table I/O functions
 203 */
 204int qed_read_l1_table_sync(BDRVQEDState *s);
 205int qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n);
 206int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,
 207                            unsigned int n);
 208int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
 209                           uint64_t offset);
 210int qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset);
 211int qed_write_l2_table(BDRVQEDState *s, QEDRequest *request,
 212                       unsigned int index, unsigned int n, bool flush);
 213int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,
 214                            unsigned int index, unsigned int n, bool flush);
 215
 216/**
 217 * Cluster functions
 218 */
 219int 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 */
 226int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);
 227
 228QEDTable *qed_alloc_table(BDRVQEDState *s);
 229
 230/**
 231 * Round down to the start of a cluster
 232 */
 233static 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
 238static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)
 239{
 240    return offset & (s->header.cluster_size - 1);
 241}
 242
 243static 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
 249static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)
 250{
 251    return pos >> s->l1_shift;
 252}
 253
 254static 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 */
 262static 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 */
 276static 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
 290static 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
 299static inline bool qed_offset_is_unalloc_cluster(uint64_t offset)
 300{
 301    if (offset == 0) {
 302        return true;
 303    }
 304    return false;
 305}
 306
 307static 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