qcow2: introduce qcow2_parse_compressed_l2_entry() helper

Add helper to parse compressed l2_entry and use it everywhere instead
of open-coding.

Note, that in most places we move to precise coffset/csize instead of
sector-aligned. Still it should work good enough for updating
refcounts.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20210914122454.141075-4-vsementsov@virtuozzo.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>

1 files changed, 17 insertions, 19 deletions

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 2734338..66cbb94 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1177,11 +1177,11 @@ void qcow2_free_any_cluster(BlockDriverState *bs, uint64_t l2_entry,
     switch (ctype) {
     case QCOW2_CLUSTER_COMPRESSED:
         {
-            int64_t offset = (l2_entry & s->cluster_offset_mask)
-                & QCOW2_COMPRESSED_SECTOR_MASK;
-            int size = QCOW2_COMPRESSED_SECTOR_SIZE *
-                (((l2_entry >> s->csize_shift) & s->csize_mask) + 1);
-            qcow2_free_clusters(bs, offset, size, type);
+            uint64_t coffset;
+            int csize;
+
+            qcow2_parse_compressed_l2_entry(bs, l2_entry, &coffset, &csize);
+            qcow2_free_clusters(bs, coffset, csize, type);
         }
         break;
     case QCOW2_CLUSTER_NORMAL:
@@ -1247,7 +1247,7 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
     bool l1_allocated = false;
     int64_t old_entry, old_l2_offset;
     unsigned slice, slice_size2, n_slices;
-    int i, j, l1_modified = 0, nb_csectors;
+    int i, j, l1_modified = 0;
     int ret;
 
     assert(addend >= -1 && addend <= 1);
@@ -1318,14 +1318,14 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
 
                     switch (qcow2_get_cluster_type(bs, entry)) {
                     case QCOW2_CLUSTER_COMPRESSED:
-                        nb_csectors = ((entry >> s->csize_shift) &
-                                       s->csize_mask) + 1;
                         if (addend != 0) {
-                            uint64_t coffset = (entry & s->cluster_offset_mask)
-                                & QCOW2_COMPRESSED_SECTOR_MASK;
+                            uint64_t coffset;
+                            int csize;
+
+                            qcow2_parse_compressed_l2_entry(bs, entry,
+                                                            &coffset, &csize);
                             ret = update_refcount(
-                                bs, coffset,
-                                nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE,
+                                bs, coffset, csize,
                                 abs(addend), addend < 0,
                                 QCOW2_DISCARD_SNAPSHOT);
                             if (ret < 0) {
@@ -1603,7 +1603,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
     BDRVQcow2State *s = bs->opaque;
     uint64_t l2_entry;
     uint64_t next_contiguous_offset = 0;
-    int i, nb_csectors, ret;
+    int i, ret;
     size_t l2_size_bytes = s->l2_size * l2_entry_size(s);
     g_autofree uint64_t *l2_table = g_malloc(l2_size_bytes);
 
@@ -1617,6 +1617,8 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
 
     /* Do the actual checks */
     for (i = 0; i < s->l2_size; i++) {
+        uint64_t coffset;
+        int csize;
         l2_entry = get_l2_entry(s, l2_table, i);
 
         switch (qcow2_get_cluster_type(bs, l2_entry)) {
@@ -1638,13 +1640,9 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
             }
 
             /* Mark cluster as used */
-            nb_csectors = ((l2_entry >> s->csize_shift) &
-                           s->csize_mask) + 1;
-            l2_entry &= s->cluster_offset_mask;
+            qcow2_parse_compressed_l2_entry(bs, l2_entry, &coffset, &csize);
             ret = qcow2_inc_refcounts_imrt(
-                bs, res, refcount_table, refcount_table_size,
-                l2_entry & QCOW2_COMPRESSED_SECTOR_MASK,
-                nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE);
+                bs, res, refcount_table, refcount_table_size, coffset, csize);
             if (ret < 0) {
                 return ret;
             }