[12/31] qcow2: Add offset_to_l1_index()

Commit Message

Alberto Garcia Oct. 12, 2017, 1:05 p.m. UTC

Similar to offset_to_l2_index(), this function returns the index in
the L1 table for a given guest offset. This is only used in a couple
of places and it's not a particularly complex calculation, but it
makes the code a bit more readable.

Although in the qcow2_get_cluster_offset() case the old code was
taking advantage of the l1_bits variable, we're going to get rid of
the other uses of l1_bits in a later patch anyway, so it doesn't make
sense to keep it just for this.

Signed-off-by: Alberto Garcia <[e-mail]>
---
 block/qcow2-cluster.c | 4 ++--
 block/qcow2.h         | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

Patch

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 45d05f86fe..f35bb20dd5 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -533,7 +533,7 @@  int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t offset,
 
     /* seek to the l2 offset in the l1 table */
 
-    l1_index = offset >> l1_bits;
+    l1_index = offset_to_l1_index(s, offset);
     if (l1_index >= s->l1_size) {
         type = QCOW2_CLUSTER_UNALLOCATED;
         goto out;
@@ -656,7 +656,7 @@  static int get_cluster_table(BlockDriverState *bs, uint64_t offset,
 
     /* seek to the l2 offset in the l1 table */
 
-    l1_index = offset >> (s->l2_bits + s->cluster_bits);
+    l1_index = offset_to_l1_index(s, offset);
     if (l1_index >= s->l1_size) {
         ret = qcow2_grow_l1_table(bs, l1_index + 1, false);
         if (ret < 0) {
diff --git a/block/qcow2.h b/block/qcow2.h
index c3ab19ddd0..61c6c27673 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -463,6 +463,11 @@  static inline int64_t size_to_l1(BDRVQcow2State *s, int64_t size)
     return (size + (1ULL << shift) - 1) >> shift;
 }
 
+static inline int offset_to_l1_index(BDRVQcow2State *s, uint64_t offset)
+{
+    return offset >> (s->l2_bits + s->cluster_bits);
+}
+
 static inline int offset_to_l2_index(BDRVQcow2State *s, int64_t offset)
 {
     return (offset >> s->cluster_bits) & (s->l2_size - 1);