qed: Add support for zero clusters
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>
diff --git a/block/qed-check.c b/block/qed-check.c
index 4600932..ea4ebc8 100644
--- a/block/qed-check.c
+++ b/block/qed-check.c
@@ -72,7 +72,8 @@
for (i = 0; i < s->table_nelems; i++) {
uint64_t offset = table->offsets[i];
- if (!offset) {
+ if (qed_offset_is_unalloc_cluster(offset) ||
+ qed_offset_is_zero_cluster(offset)) {
continue;
}
@@ -111,7 +112,7 @@
unsigned int num_invalid_l2;
uint64_t offset = table->offsets[i];
- if (!offset) {
+ if (qed_offset_is_unalloc_cluster(offset)) {
continue;
}
diff --git a/block/qed-cluster.c b/block/qed-cluster.c
index 0ec864b..3e19ad1 100644
--- a/block/qed-cluster.c
+++ b/block/qed-cluster.c
@@ -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 @@
*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 @@
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 @@
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;
}
diff --git a/block/qed.c b/block/qed.c
index 75ae244..c8c5930 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -573,7 +573,7 @@
{
QEDIsAllocatedCB *cb = opaque;
*cb->pnum = len / BDRV_SECTOR_SIZE;
- cb->is_allocated = ret == QED_CLUSTER_FOUND;
+ cb->is_allocated = (ret == QED_CLUSTER_FOUND || ret == QED_CLUSTER_ZERO);
}
static int bdrv_qed_is_allocated(BlockDriverState *bs, int64_t sector_num,
@@ -745,7 +745,10 @@
* @table: L2 table
* @index: First cluster index
* @n: Number of contiguous clusters
- * @cluster: First cluster byte offset in image file
+ * @cluster: First cluster offset
+ *
+ * The cluster offset may be an allocated byte offset in the image file, the
+ * zero cluster marker, or the unallocated cluster marker.
*/
static void qed_update_l2_table(BDRVQEDState *s, QEDTable *table, int index,
unsigned int n, uint64_t cluster)
@@ -753,7 +756,10 @@
int i;
for (i = index; i < index + n; i++) {
table->offsets[i] = cluster;
- cluster += s->header.cluster_size;
+ if (!qed_offset_is_unalloc_cluster(cluster) &&
+ !qed_offset_is_zero_cluster(cluster)) {
+ cluster += s->header.cluster_size;
+ }
}
}
@@ -1075,6 +1081,7 @@
case QED_CLUSTER_L2:
case QED_CLUSTER_L1:
+ case QED_CLUSTER_ZERO:
qed_aio_write_alloc(acb, len);
break;
@@ -1114,8 +1121,12 @@
qemu_iovec_copy(&acb->cur_qiov, acb->qiov, acb->qiov_offset, len);
- /* Handle backing file and unallocated sparse hole reads */
- if (ret != QED_CLUSTER_FOUND) {
+ /* Handle zero cluster and backing file reads */
+ if (ret == QED_CLUSTER_ZERO) {
+ qemu_iovec_memset(&acb->cur_qiov, 0, acb->cur_qiov.size);
+ qed_aio_next_io(acb, 0);
+ return;
+ } else if (ret != QED_CLUSTER_FOUND) {
qed_read_backing_file(s, acb->cur_pos, &acb->cur_qiov,
qed_aio_next_io, acb);
return;
diff --git a/block/qed.h b/block/qed.h
index 2925e37..3e1ab84 100644
--- a/block/qed.h
+++ b/block/qed.h
@@ -161,6 +161,7 @@
enum {
QED_CLUSTER_FOUND, /* cluster found */
+ QED_CLUSTER_ZERO, /* zero cluster found */
QED_CLUSTER_L2, /* cluster missing in L2 */
QED_CLUSTER_L1, /* cluster missing in L1 */
};
@@ -298,4 +299,29 @@
qed_check_cluster_offset(s, end_offset);
}
+static inline bool qed_offset_is_cluster_aligned(BDRVQEDState *s,
+ uint64_t offset)
+{
+ if (qed_offset_into_cluster(s, offset)) {
+ return false;
+ }
+ return true;
+}
+
+static inline bool qed_offset_is_unalloc_cluster(uint64_t offset)
+{
+ if (offset == 0) {
+ return true;
+ }
+ return false;
+}
+
+static inline bool qed_offset_is_zero_cluster(uint64_t offset)
+{
+ if (offset == 1) {
+ return true;
+ }
+ return false;
+}
+
#endif /* BLOCK_QED_H */
