Add a new function qcow1_read_cluster() to read a qcow cluster size data at a
time. The function qcow1_read_sector() is modified to use the function
qcow1_read_cluster().
Signed-off-by: Prasad Joshi <prasadjoshi124@xxxxxxxxx>
---
tools/kvm/qcow.c | 123 ++++++++++++++++++++++++++++++++++--------------------
1 files changed, 78 insertions(+), 45 deletions(-)
diff --git a/tools/kvm/qcow.c b/tools/kvm/qcow.c
index 9b9af86..e6d5897 100644
--- a/tools/kvm/qcow.c
+++ b/tools/kvm/qcow.c
@@ -36,68 +36,101 @@ static inline uint64_t get_cluster_offset(struct qcow *q, uint64_t offset)
return offset & ((1 << header->cluster_bits)-1);
}
-static int qcow1_read_sector(struct disk_image *self, uint64_t sector, void *dst, uint32_t dst_len)
+static uint32_t qcow1_read_cluster(struct qcow *q, uint64_t offset, void *dst, uint32_t dst_len)
{
- struct qcow *q = self->priv;
struct qcow1_header *header = q->header;
- uint64_t l2_table_offset;
- uint64_t l2_table_size;
- uint64_t clust_offset;
- uint64_t clust_start;
- uint64_t *l2_table;
- uint64_t l1_idx;
- uint64_t l2_idx;
- uint64_t offset;
-
- offset = sector << SECTOR_SHIFT;
- if (offset >= header->size)
- goto out_error;
+ struct qcow_table *table = &q->table;
+ uint32_t length;
+
+ uint32_t l2_table_size;
+ u64 l2_table_offset;
+ u64 *l2_table;
+ u64 l2_idx;
- l1_idx = get_l1_index(q, offset);
+ uint32_t clust_size;
+ u64 clust_offset;
+ u64 clust_start;
- if (l1_idx >= q->table.table_size)
- goto out_error;
+ u64 l1_idx;
- l2_table_offset = q->table.l1_table[l1_idx];
- if (!l2_table_offset)
- goto zero_sector;
+ clust_size = 1 << header->cluster_bits;
+ l2_table_size = 1 << header->l2_bits;
- l2_table_size = 1 << header->l2_bits;
+ l1_idx = get_l1_index(q, offset);
+ if (l1_idx >= table->table_size)
+ goto error;
- l2_table = calloc(l2_table_size, sizeof(uint64_t));
- if (!l2_table)
- goto out_error;
+ l2_idx = get_l2_index(q, offset);
+ if (l2_idx >= l2_table_size)
+ goto error;
- if (pread_in_full(q->fd, l2_table, sizeof(uint64_t) * l2_table_size, l2_table_offset) < 0)
- goto out_error_free_l2;
+ clust_offset = get_cluster_offset(q, offset);
+ if (clust_offset >= clust_size)
+ goto error;
- l2_idx = get_l2_index(q, offset);
+ length = clust_size - clust_offset;
+ if (length > dst_len)
+ length = dst_len;
- if (l2_idx >= l2_table_size)
- goto out_error_free_l2;
+ l2_table_offset = table->l1_table[l1_idx];
+ if (!l2_table_offset) {
+ /* unallocated level 2 table: returned zeroed data */
+ memset(dst, 0, length);
+ goto out;
+ }
- clust_start = be64_to_cpu(l2_table[l2_idx]);
+ l2_table = calloc(l2_table_size, sizeof(u64));
+ if (!l2_table)
+ goto error;
- if (!clust_start)
- goto zero_sector;
+ if (pread_in_full(q->fd, l2_table, sizeof(u64) * l2_table_size,
+ l2_table_offset) < 0)
+ goto free_l2;
- clust_offset = get_cluster_offset(q, offset);
+ clust_start = be64_to_cpu(l2_table[l2_idx]);
+ if (!clust_start) {
+ /* unalloacted cluster return zeroed data */
+ memset(dst, 0, length);
+ free(l2_table);
+ goto out;
+ }
- if (pread_in_full(q->fd, dst, dst_len, clust_start + clust_offset) < 0)
- goto out_error_free_l2;
+ if (pread_in_full(q->fd, dst, length, clust_start + clust_offset) < 0)
+ goto free_l2;
+out:
+ return length;
+free_l2:
free(l2_table);
-
+error:
return 0;
+}
-zero_sector:
- memset(dst, 0, dst_len);
+static int qcow1_read_sector(struct disk_image *self, uint64_t sector, void *dst, uint32_t dst_len)
+{
+ struct qcow *q = self->priv;
+ struct qcow1_header *header = q->header;
+ uint32_t length = 0;
+ char *buf = dst;
+ uint64_t offset;
+ uint32_t nr;
- return 0;
+ while (length < dst_len) {
+ offset = sector << SECTOR_SHIFT;
+ if (offset >= header->size)
+ goto error;
-out_error_free_l2:
- free(l2_table);
-out_error:
+ nr = qcow1_read_cluster(q, offset, buf, dst_len - length);
+ if (!nr)
+ goto error;
+
+ length += nr;
+ buf += nr;
+ sector += (nr >> SECTOR_SHIFT);
+ }
+
+ return 0;
+error:
return -1;
}
--
1.7.1
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