commit 346a53df38e29021e4a9e8c2a759b05744902857
author Max Reitz <mreitz@redhat.com> Tue Feb 10 15:28:43 2015 -0500
committer Kevin Wolf <kwolf@redhat.com> Tue Mar 10 14:02:20 2015 +0100
tree 4fb40e0b5184a98ccd17fb7d67708a7ef9c88c5b
parent 0a6ed700061fdd86b3c4b71366be42503ac2ce23

qcow2: Add two new fields to BDRVQcowState

Add two new fields regarding refcount information (the bit width of
every entry and the maximum refcount value) to the BDRVQcowState.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block/qcow2-refcount.c

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 9b80ca7..e124a54 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -584,7 +584,7 @@
 
         refcount = be16_to_cpu(refcount_block[block_index]);
         refcount += addend;
-        if (refcount < 0 || refcount > 0xffff) {
+        if (refcount < 0 || refcount > s->refcount_max) {
             ret = -EINVAL;
             goto fail;
         }
@@ -775,7 +775,7 @@
             return refcount;
         }
 
-        if (refcount == 0xffff) {
+        if (refcount == s->refcount_max) {
             offset = 0;
         }
     }

block/qcow2.c

diff --git a/block/qcow2.c b/block/qcow2.c
index 50e0a94..e04ba6d 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -684,6 +684,9 @@
         goto fail;
     }
     s->refcount_order = header.refcount_order;
+    s->refcount_bits = 1 << s->refcount_order;
+    s->refcount_max = UINT64_C(1) << (s->refcount_bits - 1);
+    s->refcount_max += s->refcount_max - 1;
 
     if (header.crypt_method > QCOW_CRYPT_AES) {
         error_setg(errp, "Unsupported encryption method: %" PRIu32,

block/qcow2.h

diff --git a/block/qcow2.h b/block/qcow2.h
index 0fee29b..55138c9 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -258,6 +258,8 @@
     int qcow_version;
     bool use_lazy_refcounts;
     int refcount_order;
+    int refcount_bits;
+    uint64_t refcount_max;
 
     bool discard_passthrough[QCOW2_DISCARD_MAX];