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/*

 * QEMU Enhanced Disk Format

 *

 * Copyright IBM, Corp. 2010

 *

 * Authors:

 *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>

 *  Anthony Liguori   <aliguori@us.ibm.com>

 *

 * This work is licensed under the terms of the GNU LGPL, version 2 or later.

 * See the COPYING.LIB file in the top-level directory.

 *

 */

#ifndef BLOCK_QED_H

#define BLOCK_QED_H

#include "block_int.h"

/* The layout of a QED file is as follows:

 *

 * +--------+----------+----------+----------+-----+

 * | header | L1 table | cluster0 | cluster1 | ... |

 * +--------+----------+----------+----------+-----+

 *

 * There is a 2-level pagetable for cluster allocation:

 *

 *                     +----------+

 *                     | L1 table |

 *                     +----------+

 *                ,------'  |  '------.

 *           +----------+   |    +----------+

 *           | L2 table |  ...   | L2 table |

 *           +----------+        +----------+

 *       ,------'  |  '------.

 *  +----------+   |    +----------+

 *  |   Data   |  ...   |   Data   |

 *  +----------+        +----------+

 *

 * The L1 table is fixed size and always present.  L2 tables are allocated on

 * demand.  The L1 table size determines the maximum possible image size; it

 * can be influenced using the cluster_size and table_size values.

 *

 * All fields are little-endian on disk.

 */

enum {

    QED_MAGIC = 'Q' | 'E' << 8 | 'D' << 16 | '\0' << 24,

    /* The image supports a backing file */

    QED_F_BACKING_FILE = 0x01,

    /* The image needs a consistency check before use */

    QED_F_NEED_CHECK = 0x02,

    /* The backing file format must not be probed, treat as raw image */

    QED_F_BACKING_FORMAT_NO_PROBE = 0x04,

    /* Feature bits must be used when the on-disk format changes */

    QED_FEATURE_MASK = QED_F_BACKING_FILE | /* supported feature bits */

                       QED_F_NEED_CHECK |

                       QED_F_BACKING_FORMAT_NO_PROBE,

    QED_COMPAT_FEATURE_MASK = 0,            /* supported compat feature bits */

    QED_AUTOCLEAR_FEATURE_MASK = 0,         /* supported autoclear feature bits */

    /* Data is stored in groups of sectors called clusters.  Cluster size must

     * be large to avoid keeping too much metadata.  I/O requests that have

     * sub-cluster size will require read-modify-write.

     */

    QED_MIN_CLUSTER_SIZE = 4 * 1024, /* in bytes */

    QED_MAX_CLUSTER_SIZE = 64 * 1024 * 1024,

    QED_DEFAULT_CLUSTER_SIZE = 64 * 1024,

    /* Allocated clusters are tracked using a 2-level pagetable.  Table size is

     * a multiple of clusters so large maximum image sizes can be supported

     * without jacking up the cluster size too much.

     */

    QED_MIN_TABLE_SIZE = 1,        /* in clusters */

    QED_MAX_TABLE_SIZE = 16,

    QED_DEFAULT_TABLE_SIZE = 4,

};

typedef struct {

    uint32_t magic;                 /* QED\0 */

    uint32_t cluster_size;          /* in bytes */

    uint32_t table_size;            /* for L1 and L2 tables, in clusters */

    uint32_t header_size;           /* in clusters */

    uint64_t features;              /* format feature bits */

    uint64_t compat_features;       /* compatible feature bits */

    uint64_t autoclear_features;    /* self-resetting feature bits */

    uint64_t l1_table_offset;       /* in bytes */

    uint64_t image_size;            /* total logical image size, in bytes */

    /* if (features & QED_F_BACKING_FILE) */

    uint32_t backing_filename_offset; /* in bytes from start of header */

    uint32_t backing_filename_size;   /* in bytes */

} QEDHeader;

typedef struct {

    uint64_t offsets[0];            /* in bytes */

} QEDTable;

/* The L2 cache is a simple write-through cache for L2 structures */

typedef struct CachedL2Table {

    QEDTable *table;

    uint64_t offset;    /* offset=0 indicates an invalidate entry */

    QTAILQ_ENTRY(CachedL2Table) node;

    int ref;

} CachedL2Table;

typedef struct {

    QTAILQ_HEAD(, CachedL2Table) entries;

    unsigned int n_entries;

} L2TableCache;

typedef struct QEDRequest {

    CachedL2Table *l2_table;

} QEDRequest;

typedef struct QEDAIOCB {

    BlockDriverAIOCB common;

    QEMUBH *bh;

    int bh_ret;                     /* final return status for completion bh */

    QSIMPLEQ_ENTRY(QEDAIOCB) next;  /* next request */

    bool is_write;                  /* false - read, true - write */

    bool *finished;                 /* signal for cancel completion */

    uint64_t end_pos;               /* request end on block device, in bytes */

    /* User scatter-gather list */

    QEMUIOVector *qiov;

    size_t qiov_offset;             /* byte count already processed */

    /* Current cluster scatter-gather list */

    QEMUIOVector cur_qiov;

    uint64_t cur_pos;               /* position on block device, in bytes */

    uint64_t cur_cluster;           /* cluster offset in image file */

    unsigned int cur_nclusters;     /* number of clusters being accessed */

    int find_cluster_ret;           /* used for L1/L2 update */

    QEDRequest request;

} QEDAIOCB;

typedef struct {

    BlockDriverState *bs;           /* device */

    uint64_t file_size;             /* length of image file, in bytes */

    QEDHeader header;               /* always cpu-endian */

    QEDTable *l1_table;

    L2TableCache l2_cache;          /* l2 table cache */

    uint32_t table_nelems;

    uint32_t l1_shift;

    uint32_t l2_shift;

    uint32_t l2_mask;

    /* Allocating write request queue */

    QSIMPLEQ_HEAD(, QEDAIOCB) allocating_write_reqs;

} BDRVQEDState;

enum {

    QED_CLUSTER_FOUND,         /* cluster found */

    QED_CLUSTER_L2,            /* cluster missing in L2 */

    QED_CLUSTER_L1,            /* cluster missing in L1 */

};

/**

 * qed_find_cluster() completion callback

 *

 * @opaque:     User data for completion callback

 * @ret:        QED_CLUSTER_FOUND   Success

 *              QED_CLUSTER_L2      Data cluster unallocated in L2

 *              QED_CLUSTER_L1      L2 unallocated in L1

 *              -errno              POSIX error occurred

 * @offset:     Data cluster offset

 * @len:        Contiguous bytes starting from cluster offset

 *

 * This function is invoked when qed_find_cluster() completes.

 *

 * On success ret is QED_CLUSTER_FOUND and offset/len are a contiguous range

 * in the image file.

 *

 * On failure ret is QED_CLUSTER_L2 or QED_CLUSTER_L1 for missing L2 or L1

 * table offset, respectively.  len is number of contiguous unallocated bytes.

 */

typedef void QEDFindClusterFunc(void *opaque, int ret, uint64_t offset, size_t len);

/**

 * Generic callback for chaining async callbacks

 */

typedef struct {

    BlockDriverCompletionFunc *cb;

    void *opaque;

} GenericCB;

void *gencb_alloc(size_t len, BlockDriverCompletionFunc *cb, void *opaque);

void gencb_complete(void *opaque, int ret);

/**

 * L2 cache functions

 */

void qed_init_l2_cache(L2TableCache *l2_cache);

void qed_free_l2_cache(L2TableCache *l2_cache);

CachedL2Table *qed_alloc_l2_cache_entry(L2TableCache *l2_cache);

void qed_unref_l2_cache_entry(CachedL2Table *entry);

CachedL2Table *qed_find_l2_cache_entry(L2TableCache *l2_cache, uint64_t offset);

void qed_commit_l2_cache_entry(L2TableCache *l2_cache, CachedL2Table *l2_table);

/**

 * Table I/O functions

 */

int qed_read_l1_table_sync(BDRVQEDState *s);

void qed_write_l1_table(BDRVQEDState *s, unsigned int index, unsigned int n,

                        BlockDriverCompletionFunc *cb, void *opaque);

int qed_write_l1_table_sync(BDRVQEDState *s, unsigned int index,

                            unsigned int n);

int qed_read_l2_table_sync(BDRVQEDState *s, QEDRequest *request,

                           uint64_t offset);

void qed_read_l2_table(BDRVQEDState *s, QEDRequest *request, uint64_t offset,

                       BlockDriverCompletionFunc *cb, void *opaque);

void qed_write_l2_table(BDRVQEDState *s, QEDRequest *request,

                        unsigned int index, unsigned int n, bool flush,

                        BlockDriverCompletionFunc *cb, void *opaque);

int qed_write_l2_table_sync(BDRVQEDState *s, QEDRequest *request,

                            unsigned int index, unsigned int n, bool flush);

/**

 * Cluster functions

 */

void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,

                      size_t len, QEDFindClusterFunc *cb, void *opaque);

/**

 * Consistency check

 */

int qed_check(BDRVQEDState *s, BdrvCheckResult *result, bool fix);

QEDTable *qed_alloc_table(BDRVQEDState *s);

/**

 * Round down to the start of a cluster

 */

static inline uint64_t qed_start_of_cluster(BDRVQEDState *s, uint64_t offset)

{

    return offset & ~(uint64_t)(s->header.cluster_size - 1);

}

static inline uint64_t qed_offset_into_cluster(BDRVQEDState *s, uint64_t offset)

{

    return offset & (s->header.cluster_size - 1);

}

static inline unsigned int qed_bytes_to_clusters(BDRVQEDState *s, size_t bytes)

{

    return qed_start_of_cluster(s, bytes + (s->header.cluster_size - 1)) /

           (s->header.cluster_size - 1);

}

static inline unsigned int qed_l1_index(BDRVQEDState *s, uint64_t pos)

{

    return pos >> s->l1_shift;

}

static inline unsigned int qed_l2_index(BDRVQEDState *s, uint64_t pos)

{

    return (pos >> s->l2_shift) & s->l2_mask;

}

/**

 * Test if a cluster offset is valid

 */

static inline bool qed_check_cluster_offset(BDRVQEDState *s, uint64_t offset)

{

    uint64_t header_size = (uint64_t)s->header.header_size *

                           s->header.cluster_size;

    if (offset & (s->header.cluster_size - 1)) {

        return false;

    }

    return offset >= header_size && offset < s->file_size;

}

/**

 * Test if a table offset is valid

 */

static inline bool qed_check_table_offset(BDRVQEDState *s, uint64_t offset)

{

    uint64_t end_offset = offset + (s->header.table_size - 1) *

                          s->header.cluster_size;

    /* Overflow check */

    if (end_offset <= offset) {

        return false;

    }

    return qed_check_cluster_offset(s, offset) &&

           qed_check_cluster_offset(s, end_offset);

}

#endif /* BLOCK_QED_H */