[Qemu-devel] [PATCH 06/29] qcow2-bitmap: add qcow2_read_bitmaps()

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Add qcow2_read_bitmaps, reading bitmap directory as specified in
docs/specs/qcow2.txt

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/qcow2-bitmap.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++++++
 block/qcow2.h        |   9 +++++
 2 files changed, 109 insertions(+)

diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index cd18b07..91ddd5f 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -25,6 +25,12 @@
  * THE SOFTWARE.
  */
 
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+
+#include "block/block_int.h"
+#include "block/qcow2.h"
+
 /* NOTICE: BME here means Bitmaps Extension and used as a namespace for
  * _internal_ constants. Please do not use this _internal_ abbreviation for
  * other needs and/or outside of this file. */
@@ -42,6 +48,100 @@
 /* bits [1, 8] U [56, 63] are reserved */
 #define BME_TABLE_ENTRY_RESERVED_MASK 0xff000000000001fe
 
+#define for_each_bitmap_header_in_dir(h, dir, size) \
+    for (h = (QCow2BitmapHeader *)(dir); \
+         h < (QCow2BitmapHeader *)((uint8_t *)(dir) + size); \
+         h = next_dir_entry(h))
+
 typedef enum BitmapType {
     BT_DIRTY_TRACKING_BITMAP = 1
 } BitmapType;
+
+static inline void bitmap_header_to_cpu(QCow2BitmapHeader *h)
+{
+    be64_to_cpus(&h->bitmap_table_offset);
+    be32_to_cpus(&h->bitmap_table_size);
+    be32_to_cpus(&h->flags);
+    be16_to_cpus(&h->name_size);
+    be32_to_cpus(&h->extra_data_size);
+}
+
+static inline int calc_dir_entry_size(size_t name_size)
+{
+    return align_offset(sizeof(QCow2BitmapHeader) + name_size, 8);
+}
+
+static inline int dir_entry_size(QCow2BitmapHeader *h)
+{
+    return calc_dir_entry_size(h->name_size);
+}
+
+static inline QCow2BitmapHeader *next_dir_entry(QCow2BitmapHeader *entry)
+{
+    return (QCow2BitmapHeader *)((uint8_t *)entry + dir_entry_size(entry));
+}
+
+/* directory_read
+ * Read bitmaps directory from bs by @offset and @size. Convert it to cpu
+ * format from BE.
+ */
+static uint8_t *directory_read(BlockDriverState *bs,
+                               uint64_t offset, uint64_t size, Error **errp)
+{
+    int ret;
+    uint8_t *dir;
+    QCow2BitmapHeader *h;
+
+    dir = g_try_malloc0(size);
+    if (dir == NULL) {
+        error_setg(errp, "Can't allocate space for bitmap directory.");
+        return NULL;
+    }
+
+    ret = bdrv_pread(bs->file, offset, dir, size);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Can't read bitmap directory.");
+        goto fail;
+    }
+
+    /* loop is safe because next entry offset is calculated after conversion to
+     * cpu format */
+    for_each_bitmap_header_in_dir(h, dir, size) {
+        bitmap_header_to_cpu(h);
+    }
+
+    if ((uint8_t *)h != dir + size) {
+        error_setg(errp, "Broken bitmap directory.");
+        goto fail;
+    }
+
+    return dir;
+
+fail:
+    g_free(dir);
+
+    return NULL;
+}
+
+int qcow2_read_bitmaps(BlockDriverState *bs, Error **errp)
+{
+    BDRVQcow2State *s = bs->opaque;
+
+    if (s->bitmap_directory != NULL) {
+        error_setg(errp, "Try read bitmaps, when they are already read.");
+        return -EEXIST;
+    }
+
+    if (s->nb_bitmaps == 0) {
+        /* No bitmaps - nothing to do */
+        return 0;
+    }
+
+    s->bitmap_directory = directory_read(bs, s->bitmap_directory_offset,
+                                         s->bitmap_directory_size, errp);
+    if (s->bitmap_directory == NULL) {
+        return -EINVAL;
+    }
+
+    return 0;
+}
diff --git a/block/qcow2.h b/block/qcow2.h
index b12cecc..7f6e023 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -292,6 +292,11 @@ typedef struct BDRVQcow2State {
     unsigned int nb_snapshots;
     QCowSnapshot *snapshots;
 
+    uint64_t bitmap_directory_offset;
+    uint64_t bitmap_directory_size;
+    uint8_t *bitmap_directory;
+    unsigned int nb_bitmaps;
+
     int flags;
     int qcow_version;
     bool use_lazy_refcounts;
@@ -599,6 +604,10 @@ int qcow2_snapshot_load_tmp(BlockDriverState *bs,
 void qcow2_free_snapshots(BlockDriverState *bs);
 int qcow2_read_snapshots(BlockDriverState *bs);
 
+/* qcow2-bitmap.c functions */
+void qcow2_free_bitmaps(BlockDriverState *bs);
+int qcow2_read_bitmaps(BlockDriverState *bs, Error **errp);
+
 /* qcow2-cache.c functions */
 Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables);
 int qcow2_cache_destroy(BlockDriverState* bs, Qcow2Cache *c);
-- 
1.8.3.1