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authorKevin Wolf <kwolf@redhat.com>2012-03-16 15:02:38 +0100
committerKevin Wolf <kwolf@redhat.com>2012-04-20 15:57:29 +0200
commit6377af48b0445e7ee50db6e0bd73a3a70098f5f4 (patch)
treee3b5171b5645490af6a392662790d7de88247a69 /block
parent6744cbab8cd63b7ce72b3eee4f0055007acf0798 (diff)
qcow2: Support reading zero clusters
This adds support for reading zero clusters in version 3 images. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
-rw-r--r--block/qcow2-cluster.c17
-rw-r--r--block/qcow2-refcount.c7
-rw-r--r--block/qcow2.c8
-rw-r--r--block/qcow2.h5
4 files changed, 33 insertions, 4 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index b8836ba009..5e5f5cf9ad 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -453,6 +453,12 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
c = 1;
*cluster_offset &= L2E_COMPRESSED_OFFSET_SIZE_MASK;
break;
+ case QCOW2_CLUSTER_ZERO:
+ c = count_contiguous_clusters(nb_clusters, s->cluster_size,
+ &l2_table[l2_index], 0,
+ QCOW_OFLAG_COMPRESSED | QCOW_OFLAG_ZERO);
+ *cluster_offset = 0;
+ break;
case QCOW2_CLUSTER_UNALLOCATED:
/* how many empty clusters ? */
c = count_contiguous_free_clusters(nb_clusters, &l2_table[l2_index]);
@@ -461,7 +467,8 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
case QCOW2_CLUSTER_NORMAL:
/* how many allocated clusters ? */
c = count_contiguous_clusters(nb_clusters, s->cluster_size,
- &l2_table[l2_index], 0, QCOW_OFLAG_COMPRESSED);
+ &l2_table[l2_index], 0,
+ QCOW_OFLAG_COMPRESSED | QCOW_OFLAG_ZERO);
*cluster_offset &= L2E_OFFSET_MASK;
break;
}
@@ -720,6 +727,7 @@ static int count_cow_clusters(BDRVQcowState *s, int nb_clusters,
break;
case QCOW2_CLUSTER_UNALLOCATED:
case QCOW2_CLUSTER_COMPRESSED:
+ case QCOW2_CLUSTER_ZERO:
break;
default:
abort();
@@ -868,9 +876,10 @@ again:
&& (cluster_offset & QCOW_OFLAG_COPIED))
{
/* We keep all QCOW_OFLAG_COPIED clusters */
- keep_clusters = count_contiguous_clusters(nb_clusters, s->cluster_size,
- &l2_table[l2_index], 0,
- QCOW_OFLAG_COPIED);
+ keep_clusters =
+ count_contiguous_clusters(nb_clusters, s->cluster_size,
+ &l2_table[l2_index], 0,
+ QCOW_OFLAG_COPIED | QCOW_OFLAG_ZERO);
assert(keep_clusters <= nb_clusters);
nb_clusters -= keep_clusters;
} else {
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 0112cc37b0..812c93c5c7 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -703,6 +703,7 @@ void qcow2_free_any_clusters(BlockDriverState *bs,
nb_clusters << s->cluster_bits);
break;
case QCOW2_CLUSTER_UNALLOCATED:
+ case QCOW2_CLUSTER_ZERO:
break;
default:
abort();
@@ -973,6 +974,12 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
l2_entry & ~511, nb_csectors * 512);
break;
+ case QCOW2_CLUSTER_ZERO:
+ if ((l2_entry & L2E_OFFSET_MASK) == 0) {
+ break;
+ }
+ /* fall through */
+
case QCOW2_CLUSTER_NORMAL:
{
/* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
diff --git a/block/qcow2.c b/block/qcow2.c
index 3e1482fa7e..9a8b354d0e 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -536,6 +536,14 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num,
}
break;
+ case QCOW2_CLUSTER_ZERO:
+ if (s->qcow_version < 3) {
+ ret = -EIO;
+ goto fail;
+ }
+ qemu_iovec_memset(&hd_qiov, 0, 512 * cur_nr_sectors);
+ break;
+
case QCOW2_CLUSTER_COMPRESSED:
/* add AIO support for compressed blocks ? */
ret = qcow2_decompress_cluster(bs, cluster_offset);
diff --git a/block/qcow2.h b/block/qcow2.h
index 2dc8ca26fb..df2bdfd0c6 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -43,6 +43,8 @@
#define QCOW_OFLAG_COPIED (1LL << 63)
/* indicate that the cluster is compressed (they never have the copied flag) */
#define QCOW_OFLAG_COMPRESSED (1LL << 62)
+/* The cluster reads as all zeros */
+#define QCOW_OFLAG_ZERO (1LL << 0)
#define REFCOUNT_SHIFT 1 /* refcount size is 2 bytes */
@@ -184,6 +186,7 @@ enum {
QCOW2_CLUSTER_UNALLOCATED,
QCOW2_CLUSTER_NORMAL,
QCOW2_CLUSTER_COMPRESSED,
+ QCOW2_CLUSTER_ZERO
};
#define L1E_OFFSET_MASK 0x00ffffffffffff00ULL
@@ -213,6 +216,8 @@ static inline int qcow2_get_cluster_type(uint64_t l2_entry)
{
if (l2_entry & QCOW_OFLAG_COMPRESSED) {
return QCOW2_CLUSTER_COMPRESSED;
+ } else if (l2_entry & QCOW_OFLAG_ZERO) {
+ return QCOW2_CLUSTER_ZERO;
} else if (!(l2_entry & L2E_OFFSET_MASK)) {
return QCOW2_CLUSTER_UNALLOCATED;
} else {