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  */
  30 static 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
  64 typedef 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
  76 static 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
 110 out:
 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  */
 135 void 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 }