qcow2: fix image creation for large, > ~2TB, images (Chris Wright)

When creating large disk images w/ qcow2 format, qcow2_create is hard
coded to creating a single refcount block.  This is insufficient for
large images, and will cause qemu-img to segfault as it walks off the
end of the refcount block.  Keep track of the space needed during image
create and create proper number of refcount blocks accordingly.

https://bugzilla.redhat.com/show_bug.cgi?id=491943Signed-off-by: NChris Wright <chrisw@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6982 c046a42c-6fe2-441c-8c8c-71466251a162

block-qcow2.c

@@ -1555,7 +1555,7 @@ static int qcow_create2(const char *filename, int64_t total_size,
 {
 
     int fd, header_size, backing_filename_len, l1_size, i, shift, l2_bits;
-    int backing_format_len = 0;
+    int ref_clusters, backing_format_len = 0;
     QCowHeader header;
     uint64_t tmp, offset;
     QCowCreateState s1, *s = &s1;
@@ -1604,22 +1604,28 @@ static int qcow_create2(const char *filename, int64_t total_size,
     offset += align_offset(l1_size * sizeof(uint64_t), s->cluster_size);
 
     s->refcount_table = qemu_mallocz(s->cluster_size);
-    s->refcount_block = qemu_mallocz(s->cluster_size);
 
     s->refcount_table_offset = offset;
     header.refcount_table_offset = cpu_to_be64(offset);
     header.refcount_table_clusters = cpu_to_be32(1);
     offset += s->cluster_size;
-
-    s->refcount_table[0] = cpu_to_be64(offset);
     s->refcount_block_offset = offset;
+
+    /* count how many refcount blocks needed */
+    tmp = offset >> s->cluster_bits;
+    ref_clusters = (tmp >> (s->cluster_bits - REFCOUNT_SHIFT)) + 1;
+    for (i=0; i < ref_clusters; i++) {
+        s->refcount_table[i] = cpu_to_be64(offset);
         offset += s->cluster_size;
+    }
+
+    s->refcount_block = qemu_mallocz(ref_clusters * s->cluster_size);
 
     /* update refcounts */
     create_refcount_update(s, 0, header_size);
     create_refcount_update(s, s->l1_table_offset, l1_size * sizeof(uint64_t));
     create_refcount_update(s, s->refcount_table_offset, s->cluster_size);
-    create_refcount_update(s, s->refcount_block_offset, s->cluster_size);
+    create_refcount_update(s, s->refcount_block_offset, ref_clusters * s->cluster_size);
 
     /* write all the data */
     write(fd, &header, sizeof(header));
@@ -1648,7 +1654,7 @@ static int qcow_create2(const char *filename, int64_t total_size,
     write(fd, s->refcount_table, s->cluster_size);
 
     lseek(fd, s->refcount_block_offset, SEEK_SET);
-    write(fd, s->refcount_block, s->cluster_size);
+    write(fd, s->refcount_block, ref_clusters * s->cluster_size);
 
     qemu_free(s->refcount_table);
     qemu_free(s->refcount_block);