[Qemu-devel] [PATCH v5 2/3] qcow2: add update refcount table realization for update_refcount

[Jun Li <junmuzi@gmail.com>]

When every item of refcount block is NULL, free refcount block and reset the
corresponding item of refcount table with NULL. At the same time, put this
cluster to s->free_cluster_index.

Signed-off-by: Jun Li <junmuzi@gmail.com>
---
v5:
  Just instead write_reftable_entry with bdrv_pwrite_sync. As write_reftable_entry has deleted from the source code.

v4:
  Do not change anything for this commit id.

v3:
  Add handle self-describing refcount blocks.
---
 block/qcow2-refcount.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 1477031..abb4f6d 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -596,6 +596,53 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
         if (refcount == 0 && s->discard_passthrough[type]) {
             update_refcount_discard(bs, cluster_offset, s->cluster_size);
         }
+
+        unsigned int refcount_table_index;
+        refcount_table_index = cluster_index >> s->refcount_block_bits;
+
+        uint64_t refcount_block_offset =
+            s->refcount_table[refcount_table_index] & REFT_OFFSET_MASK;
+
+        int64_t self_block_index = refcount_block_offset >> s->cluster_bits;
+        int self_block_index2 = (refcount_block_offset >> s->cluster_bits) &
+            ((1 << s->refcount_block_bits) - 1);
+
+        /* When refcount block is NULL, update refcount table */
+        if (!be16_to_cpu(refcount_block[0]) || self_block_index2 == 0) {
+            int k;
+            int refcount_block_entries = s->cluster_size /
+                                         sizeof(refcount_block[0]);
+            for (k = 0; k < refcount_block_entries; k++) {
+                if (k == self_block_index2) {
+                    k++;
+                }
+
+                if (be16_to_cpu(refcount_block[k])) {
+                    break;
+                }
+            }
+
+            if (k == refcount_block_entries) {
+                if (self_block_index < s->free_cluster_index) {
+                    s->free_cluster_index = self_block_index;
+                }
+
+                /* update refcount table */
+                s->refcount_table[refcount_table_index] = 0;
+                uint64_t data64 = cpu_to_be64(0);
+                ret = bdrv_pwrite_sync(bs->file,
+                                       s->refcount_table_offset +
+                                       refcount_table_index *
+                                       sizeof(uint64_t),
+                                       &data64, sizeof(data64));
+                if (ret < 0) {
+                    fprintf(stderr, "Could not update refcount table: %s\n",
+                            strerror(-ret));
+                    goto fail;
+                }
+
+            }
+        }
     }
 
     ret = 0;
@@ -1204,7 +1251,7 @@ static int check_refcounts_l2(BlockDriverState *bs, BdrvCheckResult *res,
 
         case QCOW2_CLUSTER_NORMAL:
         {
-            uint64_t offset = l2_entry & L2E_OFFSET_MASK;
+            uint64_t offset = (uint64_t)(l2_entry & L2E_OFFSET_MASK);
 
             if (flags & CHECK_FRAG_INFO) {
                 res->bfi.allocated_clusters++;
-- 
1.9.3