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