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