LXR qemu/block/qed-cluster.c

   1/*
   2 * QEMU Enhanced Disk Format Cluster functions
   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#include "qemu/osdep.h"
  16#include "qed.h"
  17
  18/**
  19 * Count the number of contiguous data clusters
  20 *
  21 * @s:              QED state
  22 * @table:          L2 table
  23 * @index:          First cluster index
  24 * @n:              Maximum number of clusters
  25 * @offset:         Set to first cluster offset
  26 *
  27 * This function scans tables for contiguous clusters.  A contiguous run of
  28 * clusters may be allocated, unallocated, or zero.
  29 */
  30static unsigned int qed_count_contiguous_clusters(BDRVQEDState *s,
  31                                                  QEDTable *table,
  32                                                  unsigned int index,
  33                                                  unsigned int n,
  34                                                  uint64_t *offset)
  35{
  36    unsigned int end = MIN(index + n, s->table_nelems);
  37    uint64_t last = table->offsets[index];
  38    unsigned int i;
  39
  40    *offset = last;
  41
  42    for (i = index + 1; i < end; i++) {
  43        if (qed_offset_is_unalloc_cluster(last)) {
  44            /* Counting unallocated clusters */
  45            if (!qed_offset_is_unalloc_cluster(table->offsets[i])) {
  46                break;
  47            }
  48        } else if (qed_offset_is_zero_cluster(last)) {
  49            /* Counting zero clusters */
  50            if (!qed_offset_is_zero_cluster(table->offsets[i])) {
  51                break;
  52            }
  53        } else {
  54            /* Counting allocated clusters */
  55            if (table->offsets[i] != last + s->header.cluster_size) {
  56                break;
  57            }
  58            last = table->offsets[i];
  59        }
  60    }
  61    return i - index;
  62}
  63
  64typedef struct {
  65    BDRVQEDState *s;
  66    uint64_t pos;
  67    size_t len;
  68
  69    QEDRequest *request;
  70
  71    /* User callback */
  72    QEDFindClusterFunc *cb;
  73    void *opaque;
  74} QEDFindClusterCB;
  75
  76static void qed_find_cluster_cb(void *opaque, int ret)
  77{
  78    QEDFindClusterCB *find_cluster_cb = opaque;
  79    BDRVQEDState *s = find_cluster_cb->s;
  80    QEDRequest *request = find_cluster_cb->request;
  81    uint64_t offset = 0;
  82    size_t len = 0;
  83    unsigned int index;
  84    unsigned int n;
  85
  86    if (ret) {
  87        goto out;
  88    }
  89
  90    index = qed_l2_index(s, find_cluster_cb->pos);
  91    n = qed_bytes_to_clusters(s,
  92                              qed_offset_into_cluster(s, find_cluster_cb->pos) +
  93                              find_cluster_cb->len);
  94    n = qed_count_contiguous_clusters(s, request->l2_table->table,
  95                                      index, n, &offset);
  96
  97    if (qed_offset_is_unalloc_cluster(offset)) {
  98        ret = QED_CLUSTER_L2;
  99    } else if (qed_offset_is_zero_cluster(offset)) {
 100        ret = QED_CLUSTER_ZERO;
 101    } else if (qed_check_cluster_offset(s, offset)) {
 102        ret = QED_CLUSTER_FOUND;
 103    } else {
 104        ret = -EINVAL;
 105    }
 106
 107    len = MIN(find_cluster_cb->len, n * s->header.cluster_size -
 108              qed_offset_into_cluster(s, find_cluster_cb->pos));
 109
 110out:
 111    find_cluster_cb->cb(find_cluster_cb->opaque, ret, offset, len);
 112    g_free(find_cluster_cb);
 113}
 114
 115/**
 116 * Find the offset of a data cluster
 117 *
 118 * @s:          QED state
 119 * @request:    L2 cache entry
 120 * @pos:        Byte position in device
 121 * @len:        Number of bytes
 122 * @cb:         Completion function
 123 * @opaque:     User data for completion function
 124 *
 125 * This function translates a position in the block device to an offset in the
 126 * image file.  It invokes the cb completion callback to report back the
 127 * translated offset or unallocated range in the image file.
 128 *
 129 * If the L2 table exists, request->l2_table points to the L2 table cache entry
 130 * and the caller must free the reference when they are finished.  The cache
 131 * entry is exposed in this way to avoid callers having to read the L2 table
 132 * again later during request processing.  If request->l2_table is non-NULL it
 133 * will be unreferenced before taking on the new cache entry.
 134 */
 135void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
 136                      size_t len, QEDFindClusterFunc *cb, void *opaque)
 137{
 138    QEDFindClusterCB *find_cluster_cb;
 139    uint64_t l2_offset;
 140
 141    /* Limit length to L2 boundary.  Requests are broken up at the L2 boundary
 142     * so that a request acts on one L2 table at a time.
 143     */
 144    len = MIN(len, (((pos >> s->l1_shift) + 1) << s->l1_shift) - pos);
 145
 146    l2_offset = s->l1_table->offsets[qed_l1_index(s, pos)];
 147    if (qed_offset_is_unalloc_cluster(l2_offset)) {
 148        cb(opaque, QED_CLUSTER_L1, 0, len);
 149        return;
 150    }
 151    if (!qed_check_table_offset(s, l2_offset)) {
 152        cb(opaque, -EINVAL, 0, 0);
 153        return;
 154    }
 155
 156    find_cluster_cb = g_malloc(sizeof(*find_cluster_cb));
 157    find_cluster_cb->s = s;
 158    find_cluster_cb->pos = pos;
 159    find_cluster_cb->len = len;
 160    find_cluster_cb->cb = cb;
 161    find_cluster_cb->opaque = opaque;
 162    find_cluster_cb->request = request;
 163
 164    qed_read_l2_table(s, request, l2_offset,
 165                      qed_find_cluster_cb, find_cluster_cb);
 166}
 167