[Qemu-devel] [PATCH 0/2] Improve qemu-img check output

[Qemu-devel] [PATCH 0/2] Improve qemu-img check output

[Kevin Wolf]

qemu-img check produces messages that are hard to understand. Even worse is
that in the end it just says something like "42 errors" with no further
explanation. Recently I got bug reports from people who though that their image
was corrupted, when in fact there were only a few leaked clusters after a
crash.

This series tries to tell the user if it's real corruption, leaked clusters or
something that went wrong during the check.

Kevin Wolf (2):
  qemu-img check: Distinguish different kinds of errors
  qcow2/vdi: Change check to distinguish error cases

 block.c                |    9 ++-
 block.h                |   10 ++++-
 block/qcow2-refcount.c |  120 ++++++++++++++++++++++++++----------------------
 block/qcow2.c          |    4 +-
 block/qcow2.h          |    2 +-
 block/vdi.c            |   10 ++--
 block_int.h            |    7 ++-
 qemu-img.c             |   62 +++++++++++++++++++------
 8 files changed, 140 insertions(+), 84 deletions(-)

[Qemu-devel] [PATCH 1/2] qemu-img check: Distinguish different kinds of errors

[Kevin Wolf]

People think that their images are corrupted when in fact there are just some
leaked clusters. Differentiating several error cases should make the messages
more comprehensible.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c    |   10 ++++++--
 block.h    |   10 ++++++++-
 qemu-img.c |   62 +++++++++++++++++++++++++++++++++++++++++++++--------------
 3 files changed, 63 insertions(+), 19 deletions(-)

diff --git a/block.c b/block.c
index dd6dd76..b0ceef0 100644
--- a/block.c
+++ b/block.c
@@ -710,15 +710,19 @@ DeviceState *bdrv_get_attached(BlockDriverState *bs)
 /*
  * Run consistency checks on an image
  *
- * Returns the number of errors or -errno when an internal error occurs
+ * Returns 0 if the check could be completed (it doesn't mean that the image is
+ * free of errors) or -errno when an internal error occured. The results of the
+ * check are stored in res.
  */
-int bdrv_check(BlockDriverState *bs)
+int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res)
 {
     if (bs->drv->bdrv_check == NULL) {
         return -ENOTSUP;
     }
 
-    return bs->drv->bdrv_check(bs);
+    memset(res, 0, sizeof(*res));
+    res->corruptions = bs->drv->bdrv_check(bs);
+    return res->corruptions < 0 ? res->corruptions : 0;
 }
 
 /* commit COW file into the raw image */
diff --git a/block.h b/block.h
index 3d03b3e..c2a7e4c 100644
--- a/block.h
+++ b/block.h
@@ -74,7 +74,6 @@ void bdrv_close(BlockDriverState *bs);
 int bdrv_attach(BlockDriverState *bs, DeviceState *qdev);
 void bdrv_detach(BlockDriverState *bs, DeviceState *qdev);
 DeviceState *bdrv_get_attached(BlockDriverState *bs);
-int bdrv_check(BlockDriverState *bs);
 int bdrv_read(BlockDriverState *bs, int64_t sector_num,
               uint8_t *buf, int nb_sectors);
 int bdrv_write(BlockDriverState *bs, int64_t sector_num,
@@ -97,6 +96,15 @@ int bdrv_change_backing_file(BlockDriverState *bs,
     const char *backing_file, const char *backing_fmt);
 void bdrv_register(BlockDriver *bdrv);
 
+
+typedef struct BdrvCheckResult {
+    int corruptions;
+    int leaks;
+    int check_errors;
+} BdrvCheckResult;
+
+int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res);
+
 /* async block I/O */
 typedef struct BlockDriverAIOCB BlockDriverAIOCB;
 typedef void BlockDriverCompletionFunc(void *opaque, int ret);
diff --git a/qemu-img.c b/qemu-img.c
index 700af21..1782ac9 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -425,11 +425,20 @@ out:
     return 0;
 }
 
+/*
+ * Checks an image for consistency. Exit codes:
+ *
+ * 0 - Check completed, image is good
+ * 1 - Check not completed because of internal errors
+ * 2 - Check completed, image is corrupted
+ * 3 - Check completed, image has leaked clusters, but is good otherwise
+ */
 static int img_check(int argc, char **argv)
 {
     int c, ret;
     const char *filename, *fmt;
     BlockDriverState *bs;
+    BdrvCheckResult result;
 
     fmt = NULL;
     for(;;) {
@@ -453,28 +462,51 @@ static int img_check(int argc, char **argv)
     if (!bs) {
         return 1;
     }
-    ret = bdrv_check(bs);
-    switch(ret) {
-    case 0:
-        printf("No errors were found on the image.\n");
-        break;
-    case -ENOTSUP:
+    ret = bdrv_check(bs, &result);
+
+    if (ret == -ENOTSUP) {
         error("This image format does not support checks");
-        break;
-    default:
-        if (ret < 0) {
-            error("An error occurred during the check");
-        } else {
-            printf("%d errors were found on the image.\n", ret);
+        return 1;
+    }
+
+    if (!(result.corruptions || result.leaks || result.check_errors)) {
+        printf("No errors were found on the image.\n");
+    } else {
+        if (result.corruptions) {
+            printf("\n%d errors were found on the image.\n"
+                "Data may be corrupted, or further writes to the image "
+                "may corrupt it.\n",
+                result.corruptions);
+        }
+
+        if (result.leaks) {
+            printf("\n%d leaked clusters were found on the image.\n"
+                "This means waste of disk space, but no harm to data.\n",
+                result.leaks);
+        }
+
+        if (result.check_errors) {
+            printf("\n%d internal errors have occurred during the check.\n",
+                result.check_errors);
         }
-        break;
     }
 
     bdrv_delete(bs);
-    if (ret) {
+
+    if (ret < 0 || result.check_errors) {
+        printf("\nAn error has occurred during the check: %s\n"
+            "The check is not complete and may have missed error.\n",
+            strerror(-ret));
         return 1;
     }
-    return 0;
+
+    if (result.corruptions) {
+        return 2;
+    } else if (result.leaks) {
+        return 3;
+    } else {
+        return 0;
+    }
 }
 
 static int img_commit(int argc, char **argv)
-- 
1.6.6.1

Re: [Qemu-devel] [PATCH 1/2] qemu-img check: Distinguish different kinds of errors

[MORITA Kazutaka]

At Fri,  2 Jul 2010 19:14:59 +0200,
Kevin Wolf wrote:
> 
> People think that their images are corrupted when in fact there are just some
> leaked clusters. Differentiating several error cases should make the messages
> more comprehensible.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c    |   10 ++++++--
>  block.h    |   10 ++++++++-
>  qemu-img.c |   62 +++++++++++++++++++++++++++++++++++++++++++++--------------
>  3 files changed, 63 insertions(+), 19 deletions(-)
> 
> diff --git a/block.c b/block.c
> index dd6dd76..b0ceef0 100644
> --- a/block.c
> +++ b/block.c
> @@ -710,15 +710,19 @@ DeviceState *bdrv_get_attached(BlockDriverState *bs)
>  /*
>   * Run consistency checks on an image
>   *
> - * Returns the number of errors or -errno when an internal error occurs
> + * Returns 0 if the check could be completed (it doesn't mean that the image is
> + * free of errors) or -errno when an internal error occured. The results of the
> + * check are stored in res.
>   */
> -int bdrv_check(BlockDriverState *bs)
> +int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res)
>  {
>      if (bs->drv->bdrv_check == NULL) {
>          return -ENOTSUP;
>      }
>  
> -    return bs->drv->bdrv_check(bs);
> +    memset(res, 0, sizeof(*res));
> +    res->corruptions = bs->drv->bdrv_check(bs);
> +    return res->corruptions < 0 ? res->corruptions : 0;
>  }
>  
>  /* commit COW file into the raw image */
> diff --git a/block.h b/block.h
> index 3d03b3e..c2a7e4c 100644
> --- a/block.h
> +++ b/block.h
> @@ -74,7 +74,6 @@ void bdrv_close(BlockDriverState *bs);
>  int bdrv_attach(BlockDriverState *bs, DeviceState *qdev);
>  void bdrv_detach(BlockDriverState *bs, DeviceState *qdev);
>  DeviceState *bdrv_get_attached(BlockDriverState *bs);
> -int bdrv_check(BlockDriverState *bs);
>  int bdrv_read(BlockDriverState *bs, int64_t sector_num,
>                uint8_t *buf, int nb_sectors);
>  int bdrv_write(BlockDriverState *bs, int64_t sector_num,
> @@ -97,6 +96,15 @@ int bdrv_change_backing_file(BlockDriverState *bs,
>      const char *backing_file, const char *backing_fmt);
>  void bdrv_register(BlockDriver *bdrv);
>  
> +
> +typedef struct BdrvCheckResult {
> +    int corruptions;
> +    int leaks;
> +    int check_errors;
> +} BdrvCheckResult;
> +
> +int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res);
> +
>  /* async block I/O */
>  typedef struct BlockDriverAIOCB BlockDriverAIOCB;
>  typedef void BlockDriverCompletionFunc(void *opaque, int ret);
> diff --git a/qemu-img.c b/qemu-img.c
> index 700af21..1782ac9 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -425,11 +425,20 @@ out:
>      return 0;
>  }
>  
> +/*
> + * Checks an image for consistency. Exit codes:
> + *
> + * 0 - Check completed, image is good
> + * 1 - Check not completed because of internal errors
> + * 2 - Check completed, image is corrupted
> + * 3 - Check completed, image has leaked clusters, but is good otherwise
> + */
>  static int img_check(int argc, char **argv)
>  {
>      int c, ret;
>      const char *filename, *fmt;
>      BlockDriverState *bs;
> +    BdrvCheckResult result;
>  
>      fmt = NULL;
>      for(;;) {
> @@ -453,28 +462,51 @@ static int img_check(int argc, char **argv)
>      if (!bs) {
>          return 1;
>      }
> -    ret = bdrv_check(bs);
> -    switch(ret) {
> -    case 0:
> -        printf("No errors were found on the image.\n");
> -        break;
> -    case -ENOTSUP:
> +    ret = bdrv_check(bs, &result);
> +
> +    if (ret == -ENOTSUP) {
>          error("This image format does not support checks");
> -        break;
> -    default:
> -        if (ret < 0) {
> -            error("An error occurred during the check");
> -        } else {
> -            printf("%d errors were found on the image.\n", ret);
> +        return 1;

Is it okay to call bdrv_delete(bs) before return?  It is necessary for
the sheepdog driver to pass qemu-iotests.

Kazutaka


--- a/qemu-img.c
+++ b/qemu-img.c
@@ -466,6 +466,7 @@ static int img_check(int argc, char **argv)
 
     if (ret == -ENOTSUP) {
         error("This image format does not support checks");
+        bdrv_delete(bs);
         return 1;
     }
 

Re: [Qemu-devel] [PATCH 1/2] qemu-img check: Distinguish different kinds of errors

[Kevin Wolf]

Am 06.07.2010 12:51, schrieb MORITA Kazutaka:
> At Fri,  2 Jul 2010 19:14:59 +0200,
> Kevin Wolf wrote:
>>
>> People think that their images are corrupted when in fact there are just some
>> leaked clusters. Differentiating several error cases should make the messages
>> more comprehensible.
>>
>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>> ---
>>  block.c    |   10 ++++++--
>>  block.h    |   10 ++++++++-
>>  qemu-img.c |   62 +++++++++++++++++++++++++++++++++++++++++++++--------------
>>  3 files changed, 63 insertions(+), 19 deletions(-)

>> @@ -453,28 +462,51 @@ static int img_check(int argc, char **argv)
>>      if (!bs) {
>>          return 1;
>>      }
>> -    ret = bdrv_check(bs);
>> -    switch(ret) {
>> -    case 0:
>> -        printf("No errors were found on the image.\n");
>> -        break;
>> -    case -ENOTSUP:
>> +    ret = bdrv_check(bs, &result);
>> +
>> +    if (ret == -ENOTSUP) {
>>          error("This image format does not support checks");
>> -        break;
>> -    default:
>> -        if (ret < 0) {
>> -            error("An error occurred during the check");
>> -        } else {
>> -            printf("%d errors were found on the image.\n", ret);
>> +        return 1;
> 
> Is it okay to call bdrv_delete(bs) before return?  It is necessary for
> the sheepdog driver to pass qemu-iotests.
> 
> Kazutaka

Yes, you're right. Thanks for catching this, I'll send a new version.

Kevin

[Qemu-devel] [PATCH v2 1/2] qemu-img check: Distinguish different kinds of errors

[Kevin Wolf]

People think that their images are corrupted when in fact there are just some
leaked clusters. Differentiating several error cases should make the messages
more comprehensible.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---

v2:
- Call bdrv_delete in -ENOTSUP case, too

 block.c    |   10 ++++++--
 block.h    |   10 ++++++++-
 qemu-img.c |   63 +++++++++++++++++++++++++++++++++++++++++++++--------------
 3 files changed, 64 insertions(+), 19 deletions(-)

diff --git a/block.c b/block.c
index dd6dd76..b0ceef0 100644
--- a/block.c
+++ b/block.c
@@ -710,15 +710,19 @@ DeviceState *bdrv_get_attached(BlockDriverState *bs)
 /*
  * Run consistency checks on an image
  *
- * Returns the number of errors or -errno when an internal error occurs
+ * Returns 0 if the check could be completed (it doesn't mean that the image is
+ * free of errors) or -errno when an internal error occured. The results of the
+ * check are stored in res.
  */
-int bdrv_check(BlockDriverState *bs)
+int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res)
 {
     if (bs->drv->bdrv_check == NULL) {
         return -ENOTSUP;
     }
 
-    return bs->drv->bdrv_check(bs);
+    memset(res, 0, sizeof(*res));
+    res->corruptions = bs->drv->bdrv_check(bs);
+    return res->corruptions < 0 ? res->corruptions : 0;
 }
 
 /* commit COW file into the raw image */
diff --git a/block.h b/block.h
index 3d03b3e..c2a7e4c 100644
--- a/block.h
+++ b/block.h
@@ -74,7 +74,6 @@ void bdrv_close(BlockDriverState *bs);
 int bdrv_attach(BlockDriverState *bs, DeviceState *qdev);
 void bdrv_detach(BlockDriverState *bs, DeviceState *qdev);
 DeviceState *bdrv_get_attached(BlockDriverState *bs);
-int bdrv_check(BlockDriverState *bs);
 int bdrv_read(BlockDriverState *bs, int64_t sector_num,
               uint8_t *buf, int nb_sectors);
 int bdrv_write(BlockDriverState *bs, int64_t sector_num,
@@ -97,6 +96,15 @@ int bdrv_change_backing_file(BlockDriverState *bs,
     const char *backing_file, const char *backing_fmt);
 void bdrv_register(BlockDriver *bdrv);
 
+
+typedef struct BdrvCheckResult {
+    int corruptions;
+    int leaks;
+    int check_errors;
+} BdrvCheckResult;
+
+int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res);
+
 /* async block I/O */
 typedef struct BlockDriverAIOCB BlockDriverAIOCB;
 typedef void BlockDriverCompletionFunc(void *opaque, int ret);
diff --git a/qemu-img.c b/qemu-img.c
index 700af21..e300f91 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -425,11 +425,20 @@ out:
     return 0;
 }
 
+/*
+ * Checks an image for consistency. Exit codes:
+ *
+ * 0 - Check completed, image is good
+ * 1 - Check not completed because of internal errors
+ * 2 - Check completed, image is corrupted
+ * 3 - Check completed, image has leaked clusters, but is good otherwise
+ */
 static int img_check(int argc, char **argv)
 {
     int c, ret;
     const char *filename, *fmt;
     BlockDriverState *bs;
+    BdrvCheckResult result;
 
     fmt = NULL;
     for(;;) {
@@ -453,28 +462,52 @@ static int img_check(int argc, char **argv)
     if (!bs) {
         return 1;
     }
-    ret = bdrv_check(bs);
-    switch(ret) {
-    case 0:
-        printf("No errors were found on the image.\n");
-        break;
-    case -ENOTSUP:
+    ret = bdrv_check(bs, &result);
+
+    if (ret == -ENOTSUP) {
         error("This image format does not support checks");
-        break;
-    default:
-        if (ret < 0) {
-            error("An error occurred during the check");
-        } else {
-            printf("%d errors were found on the image.\n", ret);
+        bdrv_delete(bs);
+        return 1;
+    }
+
+    if (!(result.corruptions || result.leaks || result.check_errors)) {
+        printf("No errors were found on the image.\n");
+    } else {
+        if (result.corruptions) {
+            printf("\n%d errors were found on the image.\n"
+                "Data may be corrupted, or further writes to the image "
+                "may corrupt it.\n",
+                result.corruptions);
+        }
+
+        if (result.leaks) {
+            printf("\n%d leaked clusters were found on the image.\n"
+                "This means waste of disk space, but no harm to data.\n",
+                result.leaks);
+        }
+
+        if (result.check_errors) {
+            printf("\n%d internal errors have occurred during the check.\n",
+                result.check_errors);
         }
-        break;
     }
 
     bdrv_delete(bs);
-    if (ret) {
+
+    if (ret < 0 || result.check_errors) {
+        printf("\nAn error has occurred during the check: %s\n"
+            "The check is not complete and may have missed error.\n",
+            strerror(-ret));
         return 1;
     }
-    return 0;
+
+    if (result.corruptions) {
+        return 2;
+    } else if (result.leaks) {
+        return 3;
+    } else {
+        return 0;
+    }
 }
 
 static int img_commit(int argc, char **argv)
-- 
1.6.6.1

[Qemu-devel] [PATCH 2/2] qcow2/vdi: Change check to distinguish error cases

[Kevin Wolf]

This distinguishes between harmless leaks and real corruption. Hopefully users
better understand what qemu-img check wants to tell them.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c                |    3 +-
 block/qcow2-refcount.c |  120 ++++++++++++++++++++++++++----------------------
 block/qcow2.c          |    4 +-
 block/qcow2.h          |    2 +-
 block/vdi.c            |   10 ++--
 block_int.h            |    7 ++-
 6 files changed, 79 insertions(+), 67 deletions(-)

diff --git a/block.c b/block.c
index b0ceef0..65cf4dc 100644
--- a/block.c
+++ b/block.c
@@ -721,8 +721,7 @@ int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res)
     }
 
     memset(res, 0, sizeof(*res));
-    res->corruptions = bs->drv->bdrv_check(bs);
-    return res->corruptions < 0 ? res->corruptions : 0;
+    return bs->drv->bdrv_check(bs, res);
 }
 
 /* commit COW file into the raw image */
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 4a96d98..4c19e7e 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -884,9 +884,10 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
  * This is used to construct a temporary refcount table out of L1 and L2 tables
  * which can be compared the the refcount table saved in the image.
  *
- * Returns the number of errors in the image that were found
+ * Modifies the number of errors in res.
  */
-static int inc_refcounts(BlockDriverState *bs,
+static void inc_refcounts(BlockDriverState *bs,
+                          BdrvCheckResult *res,
                           uint16_t *refcount_table,
                           int refcount_table_size,
                           int64_t offset, int64_t size)
@@ -894,30 +895,32 @@ static int inc_refcounts(BlockDriverState *bs,
     BDRVQcowState *s = bs->opaque;
     int64_t start, last, cluster_offset;
     int k;
-    int errors = 0;
 
     if (size <= 0)
-        return 0;
+        return;
 
     start = offset & ~(s->cluster_size - 1);
     last = (offset + size - 1) & ~(s->cluster_size - 1);
     for(cluster_offset = start; cluster_offset <= last;
         cluster_offset += s->cluster_size) {
         k = cluster_offset >> s->cluster_bits;
-        if (k < 0 || k >= refcount_table_size) {
+        if (k < 0) {
             fprintf(stderr, "ERROR: invalid cluster offset=0x%" PRIx64 "\n",
                 cluster_offset);
-            errors++;
+            res->corruptions++;
+        } else if (k >= refcount_table_size) {
+            fprintf(stderr, "Warning: cluster offset=0x%" PRIx64 " is after "
+                "the end of the image file, can't properly check refcounts.\n",
+                cluster_offset);
+            res->check_errors++;
         } else {
             if (++refcount_table[k] == 0) {
                 fprintf(stderr, "ERROR: overflow cluster offset=0x%" PRIx64
                     "\n", cluster_offset);
-                errors++;
+                res->corruptions++;
             }
         }
     }
-
-    return errors;
 }
 
 /*
@@ -928,14 +931,13 @@ static int inc_refcounts(BlockDriverState *bs,
  * Returns the number of errors found by the checks or -errno if an internal
  * error occurred.
  */
-static int check_refcounts_l2(BlockDriverState *bs,
+static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
     uint16_t *refcount_table, int refcount_table_size, int64_t l2_offset,
     int check_copied)
 {
     BDRVQcowState *s = bs->opaque;
     uint64_t *l2_table, offset;
     int i, l2_size, nb_csectors, refcount;
-    int errors = 0;
 
     /* Read L2 table from disk */
     l2_size = s->l2_size * sizeof(uint64_t);
@@ -955,16 +957,15 @@ static int check_refcounts_l2(BlockDriverState *bs,
                         "copied flag must never be set for compressed "
                         "clusters\n", offset >> s->cluster_bits);
                     offset &= ~QCOW_OFLAG_COPIED;
-                    errors++;
+                    res->corruptions++;
                 }
 
                 /* Mark cluster as used */
                 nb_csectors = ((offset >> s->csize_shift) &
                                s->csize_mask) + 1;
                 offset &= s->cluster_offset_mask;
-                errors += inc_refcounts(bs, refcount_table,
-                              refcount_table_size,
-                              offset & ~511, nb_csectors * 512);
+                inc_refcounts(bs, res, refcount_table, refcount_table_size,
+                    offset & ~511, nb_csectors * 512);
             } else {
                 /* QCOW_OFLAG_COPIED must be set iff refcount == 1 */
                 if (check_copied) {
@@ -974,35 +975,35 @@ static int check_refcounts_l2(BlockDriverState *bs,
                     if (refcount < 0) {
                         fprintf(stderr, "Can't get refcount for offset %"
                             PRIx64 ": %s\n", entry, strerror(-refcount));
+                        goto fail;
                     }
                     if ((refcount == 1) != ((entry & QCOW_OFLAG_COPIED) != 0)) {
                         fprintf(stderr, "ERROR OFLAG_COPIED: offset=%"
                             PRIx64 " refcount=%d\n", entry, refcount);
-                        errors++;
+                        res->corruptions++;
                     }
                 }
 
                 /* Mark cluster as used */
                 offset &= ~QCOW_OFLAG_COPIED;
-                errors += inc_refcounts(bs, refcount_table,
-                              refcount_table_size,
-                              offset, s->cluster_size);
+                inc_refcounts(bs, res, refcount_table,refcount_table_size,
+                    offset, s->cluster_size);
 
                 /* Correct offsets are cluster aligned */
                 if (offset & (s->cluster_size - 1)) {
                     fprintf(stderr, "ERROR offset=%" PRIx64 ": Cluster is not "
                         "properly aligned; L2 entry corrupted.\n", offset);
-                    errors++;
+                    res->corruptions++;
                 }
             }
         }
     }
 
     qemu_free(l2_table);
-    return errors;
+    return 0;
 
 fail:
-    fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
+    fprintf(stderr, "ERROR: I/O error in check_refcounts_l2\n");
     qemu_free(l2_table);
     return -EIO;
 }
@@ -1016,6 +1017,7 @@ fail:
  * error occurred.
  */
 static int check_refcounts_l1(BlockDriverState *bs,
+                              BdrvCheckResult *res,
                               uint16_t *refcount_table,
                               int refcount_table_size,
                               int64_t l1_table_offset, int l1_size,
@@ -1024,13 +1026,12 @@ static int check_refcounts_l1(BlockDriverState *bs,
     BDRVQcowState *s = bs->opaque;
     uint64_t *l1_table, l2_offset, l1_size2;
     int i, refcount, ret;
-    int errors = 0;
 
     l1_size2 = l1_size * sizeof(uint64_t);
 
     /* Mark L1 table as used */
-    errors += inc_refcounts(bs, refcount_table, refcount_table_size,
-                  l1_table_offset, l1_size2);
+    inc_refcounts(bs, res, refcount_table, refcount_table_size,
+        l1_table_offset, l1_size2);
 
     /* Read L1 table entries from disk */
     if (l1_size2 == 0) {
@@ -1055,42 +1056,41 @@ static int check_refcounts_l1(BlockDriverState *bs,
                 if (refcount < 0) {
                     fprintf(stderr, "Can't get refcount for l2_offset %"
                         PRIx64 ": %s\n", l2_offset, strerror(-refcount));
+                    goto fail;
                 }
                 if ((refcount == 1) != ((l2_offset & QCOW_OFLAG_COPIED) != 0)) {
                     fprintf(stderr, "ERROR OFLAG_COPIED: l2_offset=%" PRIx64
                         " refcount=%d\n", l2_offset, refcount);
-                    errors++;
+                    res->corruptions++;
                 }
             }
 
             /* Mark L2 table as used */
             l2_offset &= ~QCOW_OFLAG_COPIED;
-            errors += inc_refcounts(bs, refcount_table,
-                          refcount_table_size,
-                          l2_offset,
-                          s->cluster_size);
+            inc_refcounts(bs, res, refcount_table, refcount_table_size,
+                l2_offset, s->cluster_size);
 
             /* L2 tables are cluster aligned */
             if (l2_offset & (s->cluster_size - 1)) {
                 fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not "
                     "cluster aligned; L1 entry corrupted\n", l2_offset);
-                errors++;
+                res->corruptions++;
             }
 
             /* Process and check L2 entries */
-            ret = check_refcounts_l2(bs, refcount_table, refcount_table_size,
-                l2_offset, check_copied);
+            ret = check_refcounts_l2(bs, res, refcount_table,
+                refcount_table_size, l2_offset, check_copied);
             if (ret < 0) {
                 goto fail;
             }
-            errors += ret;
         }
     }
     qemu_free(l1_table);
-    return errors;
+    return 0;
 
 fail:
     fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
+    res->check_errors++;
     qemu_free(l1_table);
     return -EIO;
 }
@@ -1101,44 +1101,47 @@ fail:
  * Returns 0 if no errors are found, the number of errors in case the image is
  * detected as corrupted, and -errno when an internal error occured.
  */
-int qcow2_check_refcounts(BlockDriverState *bs)
+int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res)
 {
     BDRVQcowState *s = bs->opaque;
     int64_t size;
     int nb_clusters, refcount1, refcount2, i;
     QCowSnapshot *sn;
     uint16_t *refcount_table;
-    int ret, errors = 0;
+    int ret;
 
     size = bdrv_getlength(bs->file);
     nb_clusters = size_to_clusters(s, size);
     refcount_table = qemu_mallocz(nb_clusters * sizeof(uint16_t));
 
     /* header */
-    errors += inc_refcounts(bs, refcount_table, nb_clusters,
-                  0, s->cluster_size);
+    inc_refcounts(bs, res, refcount_table, nb_clusters,
+        0, s->cluster_size);
 
     /* current L1 table */
-    ret = check_refcounts_l1(bs, refcount_table, nb_clusters,
+    ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters,
                        s->l1_table_offset, s->l1_size, 1);
     if (ret < 0) {
         return ret;
     }
-    errors += ret;
 
     /* snapshots */
     for(i = 0; i < s->nb_snapshots; i++) {
         sn = s->snapshots + i;
-        check_refcounts_l1(bs, refcount_table, nb_clusters,
-                           sn->l1_table_offset, sn->l1_size, 0);
+        ret = check_refcounts_l1(bs, res, refcount_table, nb_clusters,
+            sn->l1_table_offset, sn->l1_size, 0);
+        if (ret < 0) {
+            return ret;
+        }
     }
-    errors += inc_refcounts(bs, refcount_table, nb_clusters,
-                  s->snapshots_offset, s->snapshots_size);
+    inc_refcounts(bs, res, refcount_table, nb_clusters,
+        s->snapshots_offset, s->snapshots_size);
 
     /* refcount data */
-    errors += inc_refcounts(bs, refcount_table, nb_clusters,
-                  s->refcount_table_offset,
-                  s->refcount_table_size * sizeof(uint64_t));
+    inc_refcounts(bs, res, refcount_table, nb_clusters,
+        s->refcount_table_offset,
+        s->refcount_table_size * sizeof(uint64_t));
+
     for(i = 0; i < s->refcount_table_size; i++) {
         uint64_t offset, cluster;
         offset = s->refcount_table[i];
@@ -1148,22 +1151,23 @@ int qcow2_check_refcounts(BlockDriverState *bs)
         if (offset & (s->cluster_size - 1)) {
             fprintf(stderr, "ERROR refcount block %d is not "
                 "cluster aligned; refcount table entry corrupted\n", i);
-            errors++;
+            res->corruptions++;
             continue;
         }
 
         if (cluster >= nb_clusters) {
             fprintf(stderr, "ERROR refcount block %d is outside image\n", i);
-            errors++;
+            res->corruptions++;
             continue;
         }
 
         if (offset != 0) {
-            errors += inc_refcounts(bs, refcount_table, nb_clusters,
-                          offset, s->cluster_size);
+            inc_refcounts(bs, res, refcount_table, nb_clusters,
+                offset, s->cluster_size);
             if (refcount_table[cluster] != 1) {
                 fprintf(stderr, "ERROR refcount block %d refcount=%d\n",
                     i, refcount_table[cluster]);
+                res->corruptions++;
             }
         }
     }
@@ -1174,19 +1178,25 @@ int qcow2_check_refcounts(BlockDriverState *bs)
         if (refcount1 < 0) {
             fprintf(stderr, "Can't get refcount for cluster %d: %s\n",
                 i, strerror(-refcount1));
+            res->check_errors++;
             continue;
         }
 
         refcount2 = refcount_table[i];
         if (refcount1 != refcount2) {
-            fprintf(stderr, "ERROR cluster %d refcount=%d reference=%d\n",
+            fprintf(stderr, "%s cluster %d refcount=%d reference=%d\n",
+                   refcount1 < refcount2 ? "ERROR" : "Leaked",
                    i, refcount1, refcount2);
-            errors++;
+            if (refcount1 < refcount2) {
+                res->corruptions++;
+            } else {
+                res->leaks++;
+            }
         }
     }
 
     qemu_free(refcount_table);
 
-    return errors;
+    return 0;
 }
 
diff --git a/block/qcow2.c b/block/qcow2.c
index 24651fc..f2b1b1c 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1146,9 +1146,9 @@ static int qcow_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
 }
 
 
-static int qcow_check(BlockDriverState *bs)
+static int qcow_check(BlockDriverState *bs, BdrvCheckResult *result)
 {
-    return qcow2_check_refcounts(bs);
+    return qcow2_check_refcounts(bs, result);
 }
 
 #if 0
diff --git a/block/qcow2.h b/block/qcow2.h
index c59b827..3ff162e 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -185,7 +185,7 @@ void qcow2_create_refcount_update(QCowCreateState *s, int64_t offset,
 int qcow2_update_snapshot_refcount(BlockDriverState *bs,
     int64_t l1_table_offset, int l1_size, int addend);
 
-int qcow2_check_refcounts(BlockDriverState *bs);
+int qcow2_check_refcounts(BlockDriverState *bs, BdrvCheckResult *res);
 
 /* qcow2-cluster.c functions */
 int qcow2_grow_l1_table(BlockDriverState *bs, int min_size);
diff --git a/block/vdi.c b/block/vdi.c
index ee8cc7b..f72633c 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -291,11 +291,10 @@ static void vdi_header_print(VdiHeader *header)
 }
 #endif
 
-static int vdi_check(BlockDriverState *bs)
+static int vdi_check(BlockDriverState *bs, BdrvCheckResult *res)
 {
     /* TODO: additional checks possible. */
     BDRVVdiState *s = (BDRVVdiState *)bs->opaque;
-    int n_errors = 0;
     uint32_t blocks_allocated = 0;
     uint32_t block;
     uint32_t *bmap;
@@ -315,11 +314,12 @@ static int vdi_check(BlockDriverState *bs)
                 } else {
                     fprintf(stderr, "ERROR: block index %" PRIu32
                             " also used by %" PRIu32 "\n", bmap[bmap_entry], bmap_entry);
+                    res->corruptions++;
                 }
             } else {
                 fprintf(stderr, "ERROR: block index %" PRIu32
                         " too large, is %" PRIu32 "\n", block, bmap_entry);
-                n_errors++;
+                res->corruptions++;
             }
         }
     }
@@ -327,12 +327,12 @@ static int vdi_check(BlockDriverState *bs)
         fprintf(stderr, "ERROR: allocated blocks mismatch, is %" PRIu32
                ", should be %" PRIu32 "\n",
                blocks_allocated, s->header.blocks_allocated);
-        n_errors++;
+        res->corruptions++;
     }
 
     qemu_free(bmap);
 
-    return n_errors;
+    return 0;
 }
 
 static int vdi_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
diff --git a/block_int.h b/block_int.h
index a94b801..877e1e5 100644
--- a/block_int.h
+++ b/block_int.h
@@ -119,8 +119,11 @@ struct BlockDriver {
     QEMUOptionParameter *create_options;
 
 
-    /* Returns number of errors in image, -errno for internal errors */
-    int (*bdrv_check)(BlockDriverState* bs);
+    /*
+     * Returns 0 for completed check, -errno for internal errors.
+     * The check results are stored in result.
+     */
+    int (*bdrv_check)(BlockDriverState* bs, BdrvCheckResult *result);
 
     void (*bdrv_debug_event)(BlockDriverState *bs, BlkDebugEvent event);
 
-- 
1.6.6.1