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/*

 * QEMU Enhanced Disk Format Cluster functions

 *

 * 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.

 *

 */

#include "qed.h"

/**

 * Count the number of contiguous data clusters

 *

 * @s:              QED state

 * @table:          L2 table

 * @index:          First cluster index

 * @n:              Maximum number of clusters

 * @offset:         Set to first cluster offset

 *

 * This function scans tables for contiguous allocated or free clusters.

 */

static unsigned int qed_count_contiguous_clusters(BDRVQEDState *s,

                                                  QEDTable *table,

                                                  unsigned int index,

                                                  unsigned int n,

                                                  uint64_t *offset)

{

    unsigned int end = MIN(index + n, s->table_nelems);

    uint64_t last = table->offsets[index];

    unsigned int i;

    *offset = last;

    for (i = index + 1; i < end; i++) {

        if (last == 0) {

            /* Counting free clusters */

            if (table->offsets[i] != 0) {

                break;

            }

        } else {

            /* Counting allocated clusters */

            if (table->offsets[i] != last + s->header.cluster_size) {

                break;

            }

            last = table->offsets[i];

        }

    }

    return i - index;

}

typedef struct {

    BDRVQEDState *s;

    uint64_t pos;

    size_t len;

    QEDRequest *request;

    /* User callback */

    QEDFindClusterFunc *cb;

    void *opaque;

} QEDFindClusterCB;

static void qed_find_cluster_cb(void *opaque, int ret)

{

    QEDFindClusterCB *find_cluster_cb = opaque;

    BDRVQEDState *s = find_cluster_cb->s;

    QEDRequest *request = find_cluster_cb->request;

    uint64_t offset = 0;

    size_t len = 0;

    unsigned int index;

    unsigned int n;

    if (ret) {

        goto out;

    }

    index = qed_l2_index(s, find_cluster_cb->pos);

    n = qed_bytes_to_clusters(s,

                              qed_offset_into_cluster(s, find_cluster_cb->pos) +

                              find_cluster_cb->len);

    n = qed_count_contiguous_clusters(s, request->l2_table->table,

                                      index, n, &offset);

    ret = offset ? QED_CLUSTER_FOUND : QED_CLUSTER_L2;

    len = MIN(find_cluster_cb->len, n * s->header.cluster_size -

              qed_offset_into_cluster(s, find_cluster_cb->pos));

    if (offset && !qed_check_cluster_offset(s, offset)) {

        ret = -EINVAL;

    }

out:

    find_cluster_cb->cb(find_cluster_cb->opaque, ret, offset, len);

    qemu_free(find_cluster_cb);

}

/**

 * Find the offset of a data cluster

 *

 * @s:          QED state

 * @request:    L2 cache entry

 * @pos:        Byte position in device

 * @len:        Number of bytes

 * @cb:         Completion function

 * @opaque:     User data for completion function

 *

 * This function translates a position in the block device to an offset in the

 * image file.  It invokes the cb completion callback to report back the

 * translated offset or unallocated range in the image file.

 *

 * If the L2 table exists, request->l2_table points to the L2 table cache entry

 * and the caller must free the reference when they are finished.  The cache

 * entry is exposed in this way to avoid callers having to read the L2 table

 * again later during request processing.  If request->l2_table is non-NULL it

 * will be unreferenced before taking on the new cache entry.

 */

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

                      size_t len, QEDFindClusterFunc *cb, void *opaque)

{

    QEDFindClusterCB *find_cluster_cb;

    uint64_t l2_offset;

    /* Limit length to L2 boundary.  Requests are broken up at the L2 boundary

     * so that a request acts on one L2 table at a time.

     */

    len = MIN(len, (((pos >> s->l1_shift) + 1) << s->l1_shift) - pos);

    l2_offset = s->l1_table->offsets[qed_l1_index(s, pos)];

    if (!l2_offset) {

        cb(opaque, QED_CLUSTER_L1, 0, len);

        return;

    }

    if (!qed_check_table_offset(s, l2_offset)) {

        cb(opaque, -EINVAL, 0, 0);

        return;

    }

    find_cluster_cb = qemu_malloc(sizeof(*find_cluster_cb));

    find_cluster_cb->s = s;

    find_cluster_cb->pos = pos;

    find_cluster_cb->len = len;

    find_cluster_cb->cb = cb;

    find_cluster_cb->opaque = opaque;

    find_cluster_cb->request = request;

    qed_read_l2_table(s, request, l2_offset,

                      qed_find_cluster_cb, find_cluster_cb);

}