[RFC PATCH v3 09/27] qcow2: Add l2_entry_size()

[Alberto Garcia]

qcow2 images with subclusters have 128-bit L2 entries. The first 64
bits contain the same information as traditional images and the last
64 bits form a bitmap with the status of each individual subcluster.

Because of that we cannot assume that L2 entries are sizeof(uint64_t)
anymore. This function returns the proper value for the image.

Signed-off-by: Alberto Garcia <address@hidden>
---
 block/qcow2-cluster.c  | 12 ++++++------
 block/qcow2-refcount.c | 14 ++++++++------
 block/qcow2.c          |  8 ++++----
 block/qcow2.h          |  9 +++++++++
 4 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 683c9569ad..851c7e6165 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -209,7 +209,7 @@ static int l2_load(BlockDriverState *bs, uint64_t offset,
                    uint64_t l2_offset, uint64_t **l2_slice)
 {
     BDRVQcow2State *s = bs->opaque;
-    int start_of_slice = sizeof(uint64_t) *
+    int start_of_slice = l2_entry_size(s) *
         (offset_to_l2_index(s, offset) - offset_to_l2_slice_index(s, offset));
 
     return qcow2_cache_get(bs, s->l2_table_cache, l2_offset + start_of_slice,
@@ -277,7 +277,7 @@ static int l2_allocate(BlockDriverState *bs, int l1_index)
 
     /* allocate a new l2 entry */
 
-    l2_offset = qcow2_alloc_clusters(bs, s->l2_size * sizeof(uint64_t));
+    l2_offset = qcow2_alloc_clusters(bs, s->l2_size * l2_entry_size(s));
     if (l2_offset < 0) {
         ret = l2_offset;
         goto fail;
@@ -301,7 +301,7 @@ static int l2_allocate(BlockDriverState *bs, int l1_index)
 
     /* allocate a new entry in the l2 cache */
 
-    slice_size2 = s->l2_slice_size * sizeof(uint64_t);
+    slice_size2 = s->l2_slice_size * l2_entry_size(s);
     n_slices = s->cluster_size / slice_size2;
 
     trace_qcow2_l2_allocate_get_empty(bs, l1_index);
@@ -365,7 +365,7 @@ fail:
     }
     s->l1_table[l1_index] = old_l2_offset;
     if (l2_offset > 0) {
-        qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t),
+        qcow2_free_clusters(bs, l2_offset, s->l2_size * l2_entry_size(s),
                             QCOW2_DISCARD_ALWAYS);
     }
     return ret;
@@ -708,7 +708,7 @@ static int get_cluster_table(BlockDriverState *bs, uint64_t 
offset,
 
         /* Then decrease the refcount of the old table */
         if (l2_offset) {
-            qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t),
+            qcow2_free_clusters(bs, l2_offset, s->l2_size * l2_entry_size(s),
                                 QCOW2_DISCARD_OTHER);
         }
 
@@ -1895,7 +1895,7 @@ static int expand_zero_clusters_in_l1(BlockDriverState 
*bs, uint64_t *l1_table,
     int ret;
     int i, j;
 
-    slice_size2 = s->l2_slice_size * sizeof(uint64_t);
+    slice_size2 = s->l2_slice_size * l2_entry_size(s);
     n_slices = s->cluster_size / slice_size2;
 
     if (!is_active_l1) {
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 223048569e..de85ed29a4 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1253,7 +1253,7 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
     l2_slice = NULL;
     l1_table = NULL;
     l1_size2 = l1_size * sizeof(uint64_t);
-    slice_size2 = s->l2_slice_size * sizeof(uint64_t);
+    slice_size2 = s->l2_slice_size * l2_entry_size(s);
     n_slices = s->cluster_size / slice_size2;
 
     s->cache_discards = true;
@@ -1604,7 +1604,7 @@ static int check_refcounts_l2(BlockDriverState *bs, 
BdrvCheckResult *res,
     int i, l2_size, nb_csectors, ret;
 
     /* Read L2 table from disk */
-    l2_size = s->l2_size * sizeof(uint64_t);
+    l2_size = s->l2_size * l2_entry_size(s);
     l2_table = g_malloc(l2_size);
 
     ret = bdrv_pread(bs->file, l2_offset, l2_table, l2_size);
@@ -1679,15 +1679,16 @@ static int check_refcounts_l2(BlockDriverState *bs, 
BdrvCheckResult *res,
                             fix & BDRV_FIX_ERRORS ? "Repairing" : "ERROR",
                             offset);
                     if (fix & BDRV_FIX_ERRORS) {
+                        int idx = i * (l2_entry_size(s) / sizeof(uint64_t));
                         uint64_t l2e_offset =
-                            l2_offset + (uint64_t)i * sizeof(uint64_t);
+                            l2_offset + (uint64_t)i * l2_entry_size(s);
                         int ign = active ? QCOW2_OL_ACTIVE_L2 :
                                            QCOW2_OL_INACTIVE_L2;
 
                         l2_entry = QCOW_OFLAG_ZERO;
                         set_l2_entry(s, l2_table, i, l2_entry);
                         ret = qcow2_pre_write_overlap_check(bs, ign,
-                                l2e_offset, sizeof(uint64_t), false);
+                                l2e_offset, l2_entry_size(s), false);
                         if (ret < 0) {
                             fprintf(stderr, "ERROR: Overlap check failed\n");
                             res->check_errors++;
@@ -1697,7 +1698,8 @@ static int check_refcounts_l2(BlockDriverState *bs, 
BdrvCheckResult *res,
                         }
 
                         ret = bdrv_pwrite_sync(bs->file, l2e_offset,
-                                               &l2_table[i], sizeof(uint64_t));
+                                               &l2_table[idx],
+                                               l2_entry_size(s));
                         if (ret < 0) {
                             fprintf(stderr, "ERROR: Failed to overwrite L2 "
                                     "table entry: %s\n", strerror(-ret));
@@ -1904,7 +1906,7 @@ static int check_oflag_copied(BlockDriverState *bs, 
BdrvCheckResult *res,
         }
 
         ret = bdrv_pread(bs->file, l2_offset, l2_table,
-                         s->l2_size * sizeof(uint64_t));
+                         s->l2_size * l2_entry_size(s));
         if (ret < 0) {
             fprintf(stderr, "ERROR: Could not read L2 table: %s\n",
                     strerror(-ret));
diff --git a/block/qcow2.c b/block/qcow2.c
index cbd857e9c7..e7607d90d4 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -868,7 +868,7 @@ static void read_cache_sizes(BlockDriverState *bs, QemuOpts 
*opts,
     uint64_t max_l2_entries = DIV_ROUND_UP(virtual_disk_size, s->cluster_size);
     /* An L2 table is always one cluster in size so the max cache size
      * should be a multiple of the cluster size. */
-    uint64_t max_l2_cache = ROUND_UP(max_l2_entries * sizeof(uint64_t),
+    uint64_t max_l2_cache = ROUND_UP(max_l2_entries * l2_entry_size(s),
                                      s->cluster_size);
 
     combined_cache_size_set = qemu_opt_get(opts, QCOW2_OPT_CACHE_SIZE);
@@ -1029,7 +1029,7 @@ static int qcow2_update_options_prepare(BlockDriverState 
*bs,
         }
     }
 
-    r->l2_slice_size = l2_cache_entry_size / sizeof(uint64_t);
+    r->l2_slice_size = l2_cache_entry_size / l2_entry_size(s);
     r->l2_table_cache = qcow2_cache_create(bs, l2_cache_size,
                                            l2_cache_entry_size);
     r->refcount_block_cache = qcow2_cache_create(bs, refcount_cache_size,
@@ -1423,7 +1423,7 @@ static int coroutine_fn qcow2_do_open(BlockDriverState 
*bs, QDict *options,
         bs->encrypted = true;
     }
 
-    s->l2_bits = s->cluster_bits - 3; /* L2 is always one cluster */
+    s->l2_bits = s->cluster_bits - ctz32(l2_entry_size(s));
     s->l2_size = 1 << s->l2_bits;
     /* 2^(s->refcount_order - 3) is the refcount width in bytes */
     s->refcount_block_bits = s->cluster_bits - (s->refcount_order - 3);
@@ -4115,7 +4115,7 @@ static int coroutine_fn 
qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
          *  preallocation. All that matters is that we will not have to 
allocate
          *  new refcount structures for them.) */
         nb_new_l2_tables = DIV_ROUND_UP(nb_new_data_clusters,
-                                        s->cluster_size / sizeof(uint64_t));
+                                        s->cluster_size / l2_entry_size(s));
         /* The cluster range may not be aligned to L2 boundaries, so add one L2
          * table for a potential head/tail */
         nb_new_l2_tables++;
diff --git a/block/qcow2.h b/block/qcow2.h
index 523bc489a5..8be020bb76 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -80,6 +80,10 @@
 
 #define QCOW_MAX_SUBCLUSTERS_PER_CLUSTER 32
 
+/* Size of normal and extended L2 entries */
+#define L2E_SIZE_NORMAL   (sizeof(uint64_t))
+#define L2E_SIZE_EXTENDED (sizeof(uint64_t) * 2)
+
 #define MIN_CLUSTER_BITS 9
 #define MAX_CLUSTER_BITS 21
 
@@ -506,6 +510,11 @@ static inline bool has_subclusters(BDRVQcow2State *s)
     return false;
 }
 
+static inline size_t l2_entry_size(BDRVQcow2State *s)
+{
+    return has_subclusters(s) ? L2E_SIZE_EXTENDED : L2E_SIZE_NORMAL;
+}
+
 static inline uint64_t get_l2_entry(BDRVQcow2State *s, uint64_t *l2_slice,
                                     int idx)
 {
-- 
2.20.1