[Qemu-devel] [PATCH 05/17] qcow2-dirty-bitmap: read dirty bitmap directory

[Vladimir Sementsov-Ogievskiy]

Adds qcow2_read_dirty_bitmaps, reading Dirty Bitmap Directory as
specified in docs/specs/qcow2.txt

Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
 block/qcow2-dirty-bitmap.c | 155 +++++++++++++++++++++++++++++++++++++++++++++
 block/qcow2.h              |  10 +++
 2 files changed, 165 insertions(+)

diff --git a/block/qcow2-dirty-bitmap.c b/block/qcow2-dirty-bitmap.c
index fd4e0ef..1260d1d 100644
--- a/block/qcow2-dirty-bitmap.c
+++ b/block/qcow2-dirty-bitmap.c
@@ -25,6 +25,9 @@
  * THE SOFTWARE.
  */
 
+#include "block/block_int.h"
+#include "block/qcow2.h"
+
 /* NOTICE: DBM here means Dirty Bitmap and used as a namespace for _internal_
  * constants. Please do not use this _internal_ abbreviation for other needs
  * and/or outside of this file. */
@@ -40,3 +43,155 @@
 
 /* bits [0, 8] U [56, 63] are reserved */
 #define DBM_TABLE_ENTRY_RESERVED_MASK 0xff000000000001ff
+
+void qcow2_free_dirty_bitmaps(BlockDriverState *bs)
+{
+    BDRVQcowState *s = bs->opaque;
+    int i;
+
+    for (i = 0; i < s->nb_dirty_bitmaps; i++) {
+        g_free(s->dirty_bitmaps[i].name);
+    }
+    g_free(s->dirty_bitmaps);
+    s->dirty_bitmaps = NULL;
+    s->nb_dirty_bitmaps = 0;
+
+    g_free(s->dirty_bitmap_directory);
+    s->dirty_bitmap_directory = NULL;
+}
+
+static void bitmap_header_to_cpu(QCowDirtyBitmapHeader *h)
+{
+    be64_to_cpus(&h->dirty_bitmap_table_offset);
+    be64_to_cpus(&h->nb_virtual_bits);
+    be32_to_cpus(&h->dirty_bitmap_table_size);
+    be32_to_cpus(&h->granularity_bits);
+    be32_to_cpus(&h->flags);
+    be16_to_cpus(&h->name_size);
+}
+
+static int calc_dir_entry_size(size_t name_size)
+{
+    return align_offset(sizeof(QCowDirtyBitmapHeader) + name_size, 8);
+}
+
+static int dir_entry_size(QCowDirtyBitmapHeader *h)
+{
+    return calc_dir_entry_size(h->name_size);
+}
+
+static int check_constraints(int cluster_size,
+                             QCowDirtyBitmapHeader *h)
+{
+    uint64_t phys_bitmap_bytes =
+        (uint64_t)h->dirty_bitmap_table_size * cluster_size;
+    uint64_t max_virtual_bits = (phys_bitmap_bytes * 8) << h->granularity_bits;
+
+    int fail =
+            (h->dirty_bitmap_table_offset % cluster_size) ||
+            (h->dirty_bitmap_table_size > DBM_MAX_TABLE_SIZE) ||
+            (phys_bitmap_bytes > DBM_MAX_PHYS_SIZE) ||
+            (h->nb_virtual_bits > max_virtual_bits) ||
+            (h->granularity_bits > DBM_MAX_GRANULARITY_BITS) ||
+            (h->flags & DBM_RESERVED_FLAGS) ||
+            (h->name_size > DBM_MAX_NAME_SIZE);
+
+    return fail ? -EINVAL : 0;
+}
+
+static int directory_read(BlockDriverState *bs)
+{
+    int ret;
+    BDRVQcowState *s = bs->opaque;
+    uint8_t *entry, *end;
+
+    if (s->dirty_bitmap_directory != NULL) {
+        /* already read */
+        return -EEXIST;
+    }
+
+    s->dirty_bitmap_directory = g_try_malloc0(s->dirty_bitmap_directory_size);
+    if (s->dirty_bitmap_directory == NULL) {
+        return -ENOMEM;
+    }
+
+    ret = bdrv_pread(bs->file,
+                     s->dirty_bitmap_directory_offset,
+                     s->dirty_bitmap_directory,
+                     s->dirty_bitmap_directory_size);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    entry = s->dirty_bitmap_directory;
+    end = s->dirty_bitmap_directory + s->dirty_bitmap_directory_size;
+    while (entry < end) {
+        QCowDirtyBitmapHeader *h = (QCowDirtyBitmapHeader *)entry;
+        bitmap_header_to_cpu(h);
+
+        ret = check_constraints(s->cluster_size, h);
+        if (ret < 0) {
+            goto fail;
+        }
+
+        entry += dir_entry_size(h);
+    }
+
+    return 0;
+
+fail:
+    g_free(s->dirty_bitmap_directory);
+    s->dirty_bitmap_directory = NULL;
+
+    return ret;
+}
+
+int qcow2_read_dirty_bitmaps(BlockDriverState *bs)
+{
+    int ret;
+    BDRVQcowState *s = bs->opaque;
+    size_t offset;
+    QCowDirtyBitmap *bm, *end;
+
+    if (s->dirty_bitmap_directory != NULL || s->dirty_bitmaps != NULL) {
+        /* already read */
+        return -EEXIST;
+    }
+
+    if (s->nb_dirty_bitmaps == 0) {
+        /* No bitmaps - nothing to do */
+        return 0;
+    }
+
+    ret = directory_read(bs);
+    if (ret < 0) {
+        return ret;
+    }
+
+    s->dirty_bitmaps = g_try_new0(QCowDirtyBitmap, s->nb_dirty_bitmaps);
+    if (s->dirty_bitmaps == NULL) {
+        ret = -ENOMEM;
+        goto out;
+    }
+
+    offset = 0;
+    end = s->dirty_bitmaps + s->nb_dirty_bitmaps;
+    for (bm = s->dirty_bitmaps; bm < end; ++bm) {
+        QCowDirtyBitmapHeader *h =
+                (QCowDirtyBitmapHeader *)(s->dirty_bitmap_directory + offset);
+
+        bm->offset = offset;
+        bm->name = g_malloc(h->name_size + 1);
+        memcpy(bm->name, h + 1, h->name_size);
+        bm->name[h->name_size] = '\0';
+
+        offset += dir_entry_size(h);
+    }
+    ret = 0;
+
+out:
+    if (ret < 0) {
+        qcow2_free_dirty_bitmaps(bs);
+    }
+    return ret;
+}
diff --git a/block/qcow2.h b/block/qcow2.h
index a2a5d4a..5016fa1 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -288,6 +288,12 @@ typedef struct BDRVQcowState {
     unsigned int nb_snapshots;
     QCowSnapshot *snapshots;
 
+    uint64_t dirty_bitmap_directory_offset;
+    size_t dirty_bitmap_directory_size;
+    uint8_t *dirty_bitmap_directory;
+    unsigned int nb_dirty_bitmaps;
+    QCowDirtyBitmap *dirty_bitmaps;
+
     int flags;
     int qcow_version;
     bool use_lazy_refcounts;
@@ -598,6 +604,10 @@ int qcow2_snapshot_load_tmp(BlockDriverState *bs,
 void qcow2_free_snapshots(BlockDriverState *bs);
 int qcow2_read_snapshots(BlockDriverState *bs);
 
+/* qcow2-dirty-bitmap.c functions */
+void qcow2_free_dirty_bitmaps(BlockDriverState *bs);
+int qcow2_read_dirty_bitmaps(BlockDriverState *bs);
+
 /* qcow2-cache.c functions */
 Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables);
 int qcow2_cache_destroy(BlockDriverState* bs, Qcow2Cache *c);
-- 
2.1.4