[Qemu-devel] [PATCH v7] qemu-img info lists bitmap directory entries

[Andrey Shinkevich]

In the 'Format specific information' section of the 'qemu-img info'
command output, the supplemental information about existing QCOW2
bitmaps will be shown, such as a bitmap name, flags and granularity:

image: /vz/vmprivate/VM1/harddisk.hdd
file format: qcow2
virtual size: 64G (68719476736 bytes)
disk size: 3.0M
cluster_size: 1048576
Format specific information:
    compat: 1.1
    lazy refcounts: true
    bitmaps:
        [0]:
            flags:
                [0]: in-use
                [1]: auto
            name: back-up1
            unknown flags: 4
            granularity: 65536
        [1]:
            flags:
                [0]: in-use
                [1]: auto
            name: back-up2
            unknown flags: 8
            granularity: 65536
    refcount bits: 16
    corrupt: false

Signed-off-by: Andrey Shinkevich <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
v7:
A description was added to the function qcow2_get_bitmap_info_list().
In the function qcow2_get_specific_info(), the comment was modified
so that we ignore any error in obtaining the list of bitmaps to
pass the rest of QCOW2 specific information to a caller.

v6:
'[PATCH v6] qemu-img info lists bitmap directory entries'.
The error handling logic for the bitmaps empty list was reversed.

v5:
'[PATCH v5] qemu-img info lists bitmap directory entries'.
The error handling logic for the bitmaps empty list was fixed and documented.

v4:
'[PATCH v4] qemu-img info lists bitmap directory entries'.
Unknown flags are checked with the mask BME_RESERVED_FLAGS.
The code minor refactoring was made.

v3:
'[PATCH v3] qemu-img info lists bitmap directory entries'.
Now, qcow2_get_bitmap_info_list() is invoked under the condition of QCOW
version #3 to avoid memory leaks in case of QCOW version #2.
Furthermore, qcow2_get_bitmap_info_list() checks the number of existing bitmaps.
So, if no bitmap exists, no bitmap error message is printed in the output.
The data type of the bitmap 'granularity' parameter was left as 'uint32'
because bitmap_list_load() returns error if granularity_bits is grater than 31.

v2:
'[PATCH v2] qemu-img info lists bitmap directory entries'.
The targeted version of the release at 'Since' word of the comments to the new
structures changed to 4.0 in the file qapi/block-core.json.
A comment to the 'bitmaps' new member was supplied.
The 'unknown flags' parameter was introduced to indicate presence of QCOW2
bitmap unknown flags, if any.
The word 'dirty' was removed from the code and from the comments as we list all
the bitmaps.
The 'bitmaps' printed parameter was removed for the release versions earlier
than 3.x.
The example of the output was moved above the 'Signed-off-by' line.

The first version was '[PATCH] qemu-img info lists bitmap directory entries'.

 block/qcow2-bitmap.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 block/qcow2.c        |  9 ++++++++
 block/qcow2.h        |  2 ++
 qapi/block-core.json | 42 ++++++++++++++++++++++++++++++++++-
 qemu-img.c           |  5 +++++
 5 files changed, 120 insertions(+), 1 deletion(-)

diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index accebef..8aedddc 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -1008,6 +1008,69 @@ fail:
     return false;
 }
 
+static Qcow2BitmapInfoFlagsList *get_bitmap_info_flags(uint32_t flags)
+{
+    Qcow2BitmapInfoFlagsList *list = NULL;
+    Qcow2BitmapInfoFlagsList **plist = &list;
+
+    if (flags & BME_FLAG_IN_USE) {
+        Qcow2BitmapInfoFlagsList *entry = g_new0(Qcow2BitmapInfoFlagsList, 1);
+        entry->value = QCOW2_BITMAP_INFO_FLAGS_IN_USE;
+        *plist = entry;
+        plist = &entry->next;
+    }
+    if (flags & BME_FLAG_AUTO) {
+        Qcow2BitmapInfoFlagsList *entry = g_new0(Qcow2BitmapInfoFlagsList, 1);
+        entry->value = QCOW2_BITMAP_INFO_FLAGS_AUTO;
+        *plist = entry;
+    }
+    return list;
+}
+
+/* qcow2_get_bitmap_info_list()
+ * Returns a list of QCOW2 bitmap details.
+ * In case of no bitmaps, the function returns NULL and
+ * the @errp parameter is not set (for a 0-length list in the QMP).
+ * When bitmap information can not be obtained, the function returns
+ * NULL and the @errp parameter is set (for omitting the list in QMP).
+ */
+Qcow2BitmapInfoList *qcow2_get_bitmap_info_list(BlockDriverState *bs,
+                                                Error **errp)
+{
+    BDRVQcow2State *s = bs->opaque;
+    Qcow2BitmapList *bm_list;
+    Qcow2Bitmap *bm;
+    Qcow2BitmapInfoList *list = NULL;
+    Qcow2BitmapInfoList **plist = &list;
+
+    if (s->nb_bitmaps == 0) {
+        return NULL;
+    }
+
+    bm_list = bitmap_list_load(bs, s->bitmap_directory_offset,
+                               s->bitmap_directory_size, errp);
+    if (bm_list == NULL) {
+        return NULL;
+    }
+
+    QSIMPLEQ_FOREACH(bm, bm_list, entry) {
+        Qcow2BitmapInfo *info = g_new0(Qcow2BitmapInfo, 1);
+        Qcow2BitmapInfoList *obj = g_new0(Qcow2BitmapInfoList, 1);
+        info->granularity = 1U << bm->granularity_bits;
+        info->name = g_strdup(bm->name);
+        info->flags = get_bitmap_info_flags(bm->flags);
+        info->unknown_flags = bm->flags & BME_RESERVED_FLAGS;
+        info->has_unknown_flags = !!info->unknown_flags;
+        obj->value = info;
+        *plist = obj;
+        plist = &obj->next;
+    }
+
+    bitmap_list_free(bm_list);
+
+    return list;
+}
+
 int qcow2_reopen_bitmaps_rw_hint(BlockDriverState *bs, bool *header_updated,
                                  Error **errp)
 {
diff --git a/block/qcow2.c b/block/qcow2.c
index 991d6ac..d79f667 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -4270,6 +4270,10 @@ static ImageInfoSpecific 
*qcow2_get_specific_info(BlockDriverState *bs)
             .refcount_bits      = s->refcount_bits,
         };
     } else if (s->qcow_version == 3) {
+        Qcow2BitmapInfoList *bitmaps;
+        Error *local_err = NULL;
+
+        bitmaps = qcow2_get_bitmap_info_list(bs, &local_err);
         *spec_info->u.qcow2.data = (ImageInfoSpecificQCow2){
             .compat             = g_strdup("1.1"),
             .lazy_refcounts     = s->compatible_features &
@@ -4279,7 +4283,12 @@ static ImageInfoSpecific 
*qcow2_get_specific_info(BlockDriverState *bs)
                                   QCOW2_INCOMPAT_CORRUPT,
             .has_corrupt        = true,
             .refcount_bits      = s->refcount_bits,
+            .has_bitmaps        = !local_err,
+            .bitmaps            = bitmaps,
         };
+        /* If an error occurs in obtaining bitmaps, ignore
+         * it to show other QCOW2 specific information. */
+        error_free(local_err);
     } else {
         /* if this assertion fails, this probably means a new version was
          * added without having it covered here */
diff --git a/block/qcow2.h b/block/qcow2.h
index 8662b68..0ec2b3d 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -685,6 +685,8 @@ int qcow2_check_bitmaps_refcounts(BlockDriverState *bs, 
BdrvCheckResult *res,
                                   void **refcount_table,
                                   int64_t *refcount_table_size);
 bool qcow2_load_dirty_bitmaps(BlockDriverState *bs, Error **errp);
+Qcow2BitmapInfoList *qcow2_get_bitmap_info_list(BlockDriverState *bs,
+                                                Error **errp);
 int qcow2_reopen_bitmaps_rw_hint(BlockDriverState *bs, bool *header_updated,
                                  Error **errp);
 int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index d4fe710..9898baa 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -69,6 +69,10 @@
 # @encrypt: details about encryption parameters; only set if image
 #           is encrypted (since 2.10)
 #
+# @bitmaps: A list of qcow2 bitmap details (possibly empty, such as for
+#           v2 images which do not support bitmaps); absent if bitmap
+#           information could not be obtained (since 4.0)
+#
 # Since: 1.7
 ##
 { 'struct': 'ImageInfoSpecificQCow2',
@@ -77,7 +81,8 @@
       '*lazy-refcounts': 'bool',
       '*corrupt': 'bool',
       'refcount-bits': 'int',
-      '*encrypt': 'ImageInfoSpecificQCow2Encryption'
+      '*encrypt': 'ImageInfoSpecificQCow2Encryption',
+      '*bitmaps': ['Qcow2BitmapInfo']
   } }
 
 ##
@@ -454,6 +459,41 @@
            'status': 'DirtyBitmapStatus'} }
 
 ##
+# @Qcow2BitmapInfoFlags:
+#
+# An enumeration of flags that a bitmap can report to the user.
+#
+# @in-use: The bitmap was not saved correctly and may be inconsistent.
+#
+# @auto: The bitmap must reflect all changes of the virtual disk by any
+#        application that would write to this qcow2 file.
+#
+# Since: 4.0
+##
+{ 'enum': 'Qcow2BitmapInfoFlags',
+  'data': ['in-use', 'auto'] }
+
+##
+# @Qcow2BitmapInfo:
+#
+# Qcow2 bitmap information.
+#
+# @name: the name of the bitmap
+#
+# @granularity: granularity of the bitmap in bytes
+#
+# @flags: flags of the bitmap
+#
+# @unknown-flags: unspecified flags if detected
+#
+# Since: 4.0
+##
+{ 'struct': 'Qcow2BitmapInfo',
+  'data': {'name': 'str', 'granularity': 'uint32',
+           'flags': ['Qcow2BitmapInfoFlags'],
+           '*unknown-flags': 'uint32' } }
+
+##
 # @BlockLatencyHistogramInfo:
 #
 # Block latency histogram.
diff --git a/qemu-img.c b/qemu-img.c
index ad04f59..144d7b8 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -2601,6 +2601,11 @@ static ImageInfoList *collect_image_info_list(bool 
image_opts,
             blk_unref(blk);
             goto err;
         }
+        if (info->format_specific &&
+            info->format_specific->type == IMAGE_INFO_SPECIFIC_KIND_QCOW2 &&
+            info->format_specific->u.qcow2.data->has_bitmaps == false) {
+            warn_report("Failed to load bitmap list");
+        }
 
         elem = g_new0(ImageInfoList, 1);
         elem->value = info;
-- 
1.8.3.1