[Qemu-devel] [PATCH v2] qemu-img: return allocated size for block device with qcow2 format

[Ivan Ren]

qemu-img info with a block device which has a qcow2 format always
return 0 for disk size, and this can not reflect the qcow2 size
and the used space of the block device. This patch return the
allocated size of qcow2 as the disk size.

Signed-off-by: Ivan Ren <address@hidden>
---
 block/qcow2.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

This version differs from the previous:
(1).Accumulate all non-0 refcount cluster as the allocated size instead the
highest offset.
(2).Simplify the implementation by just check the refcount info.

diff --git a/block/qcow2.c b/block/qcow2.c
index ef68772..e64469a 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4493,6 +4493,59 @@ static QemuOptsList qcow2_create_opts = {
     }
 };
 
+/* Get allocated space of qcow2, aligned to cluster_size */
+static int64_t qcow2_get_allocated_size(BlockDriverState *bs)
+{
+    int64_t allocated_cluster_count = 0;
+    uint64_t refcount;
+    int64_t i, j, begin_index, end_index;
+
+    BDRVQcow2State *s = bs->opaque;
+
+    /* Traverse refcount table */
+    for (i = 0; i < s->refcount_table_size; i++) {
+        if (s->refcount_table[i] & REFT_OFFSET_MASK) {
+            begin_index = i * s->refcount_block_size;
+            end_index = begin_index + s->refcount_block_size;
+            for (j = begin_index; j < end_index; j++) {
+                if (qcow2_get_refcount(bs, j, &refcount) < 0) {
+                    continue;
+                }
+                if (refcount > 0) {
+                    allocated_cluster_count++;
+                }
+            }
+        }
+
+    }
+
+    return allocated_cluster_count * s->cluster_size;
+}
+
+static int64_t qcow2_get_allocated_file_size(BlockDriverState *bs)
+{
+    int64_t ret = 0;
+
+    /* Get through bs->file first */
+    if (bs->file) {
+        ret = bdrv_get_allocated_file_size(bs->file->bs);
+    }
+
+    /*
+     * If ret < 0, some error may happen to the underlying media, return the
+     * error directly.
+     * If ret == 0, means length get from bs->file is 0, which is impossible
+     * for a normal file because of the qcow2 header. In this case, the
+     * underlying media may be a block device or anything else that can't
+     * return a suitable size. So we get the allocated size of qcow2 instead.
+     */
+    if (!ret) {
+        ret = qcow2_get_allocated_size(bs);
+    }
+
+    return ret;
+}
+
 BlockDriver bdrv_qcow2 = {
     .format_name        = "qcow2",
     .instance_size      = sizeof(BDRVQcow2State),
@@ -4516,6 +4569,7 @@ BlockDriver bdrv_qcow2 = {
     .bdrv_co_pwrite_zeroes  = qcow2_co_pwrite_zeroes,
     .bdrv_co_pdiscard       = qcow2_co_pdiscard,
     .bdrv_truncate          = qcow2_truncate,
+    .bdrv_get_allocated_file_size = qcow2_get_allocated_file_size,
     .bdrv_co_pwritev_compressed = qcow2_co_pwritev_compressed,
     .bdrv_make_empty        = qcow2_make_empty,
 
-- 
1.8.3.1