qemu-img: add image fragmentation statistics

Discussion can be found at:
http://patchwork.ozlabs.org/patch/128730/

This patch add image fragmentation statistics while using qemu-img check.

Signed-off-by: Dong Xu Wang <wdongxu@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.h

@@ -17,6 +17,12 @@ typedef struct BlockDriverInfo {
     int64_t vm_state_offset;
 } BlockDriverInfo;
 
+typedef struct BlockFragInfo {
+    uint64_t allocated_clusters;
+    uint64_t total_clusters;
+    uint64_t fragmented_clusters;
+} BlockFragInfo;
+
 typedef struct QEMUSnapshotInfo {
     char id_str[128]; /* unique snapshot id */
     /* the following fields are informative. They are not needed for
@@ -175,6 +181,7 @@ typedef struct BdrvCheckResult {
     int corruptions;
     int leaks;
     int check_errors;
+    BlockFragInfo bfi;
 } BdrvCheckResult;
 
 int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res);

qemu-img.c

@@ -428,6 +428,13 @@ static int img_check(int argc, char **argv)
         }
     }
 
+    if (result.bfi.total_clusters != 0 && result.bfi.allocated_clusters != 0) {
+        printf("%" PRId64 "/%" PRId64 "= %0.2f%% allocated, %0.2f%% fragmented\n",
+        result.bfi.allocated_clusters, result.bfi.total_clusters,
+        result.bfi.allocated_clusters * 100.0 / result.bfi.total_clusters,
+        result.bfi.fragmented_clusters * 100.0 / result.bfi.allocated_clusters);
+    }
+
     bdrv_delete(bs);
 
     if (ret < 0 || result.check_errors) {
@@ -716,7 +723,7 @@ static int img_convert(int argc, char **argv)
         ret = -1;
         goto out;
     }
-        
+
     qemu_progress_init(progress, 2.0);
     qemu_progress_print(0, 100);