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qed: Add support for zero clusters

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Zero clusters are similar to unallocated clusters except instead of reading
their value from a backing file when one is available, the cluster is always
read as zero.

This implements read support only.  At this stage, QED will never write a
zero cluster.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Anthony Liguori 2010-12-17 15:58:22 +00:00 • committed by Kevin Wolf
parent d54f10bba7
commit 21df65b644
4 changed files with 66 additions and 17 deletions
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31
block/qed-cluster.c
View file

@ -23,7 +23,8 @@
* @n: Maximum number of clusters
* @offset: Set to first cluster offset
*
* This function scans tables for contiguous allocated or free clusters.
* This function scans tables for contiguous clusters. A contiguous run of
* clusters may be allocated, unallocated, or zero.
*/
static unsigned int qed_count_contiguous_clusters(BDRVQEDState *s,
QEDTable *table,
@ -38,9 +39,14 @@ static unsigned int qed_count_contiguous_clusters(BDRVQEDState *s,
*offset = last;
for (i = index + 1; i < end; i++) {
if (last == 0) {
/* Counting free clusters */
if (table->offsets[i] != 0) {
if (qed_offset_is_unalloc_cluster(last)) {
/* Counting unallocated clusters */
if (!qed_offset_is_unalloc_cluster(table->offsets[i])) {
break;
}
} else if (qed_offset_is_zero_cluster(last)) {
/* Counting zero clusters */
if (!qed_offset_is_zero_cluster(table->offsets[i])) {
break;
}
} else {
@ -87,14 +93,19 @@ static void qed_find_cluster_cb(void *opaque, int ret)
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)) {
if (qed_offset_is_unalloc_cluster(offset)) {
ret = QED_CLUSTER_L2;
} else if (qed_offset_is_zero_cluster(offset)) {
ret = QED_CLUSTER_ZERO;
} else if (qed_check_cluster_offset(s, offset)) {
ret = QED_CLUSTER_FOUND;
} else {
ret = -EINVAL;
}
len = MIN(find_cluster_cb->len, n * s->header.cluster_size -
qed_offset_into_cluster(s, find_cluster_cb->pos));
out:
find_cluster_cb->cb(find_cluster_cb->opaque, ret, offset, len);
qemu_free(find_cluster_cb);
@ -132,7 +143,7 @@ void qed_find_cluster(BDRVQEDState *s, QEDRequest *request, uint64_t pos,
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) {
if (qed_offset_is_unalloc_cluster(l2_offset)) {
cb(opaque, QED_CLUSTER_L1, 0, len);
return;
}