[02/10] qcow2: compressed read: simplify cluster descriptor passing

Commit Message

Vladimir Sementsov-Ogievskiy May 4, 2021, 3:20 p.m. UTC

Let's pass the whole L2 entry and not bother with
L2E_COMPRESSED_OFFSET_SIZE_MASK.

It also helps further refactoring that adds generic
qcow2_parse_compressed_l2_entry() helper.

Signed-off-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
---
 block/qcow2.h         |  1 -
 block/qcow2-cluster.c |  5 ++---
 block/qcow2.c         | 12 +++++++-----
 3 files changed, 9 insertions(+), 9 deletions(-)

Comments

Eric Blake May 4, 2021, 7:20 p.m. UTC | #1

On 5/4/21 10:20 AM, Vladimir Sementsov-Ogievskiy wrote:
> Let's pass the whole L2 entry and not bother with
> L2E_COMPRESSED_OFFSET_SIZE_MASK.
> 
> It also helps further refactoring that adds generic
> qcow2_parse_compressed_l2_entry() helper.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <[e-mail]>
> ---
>  block/qcow2.h         |  1 -
>  block/qcow2-cluster.c |  5 ++---
>  block/qcow2.c         | 12 +++++++-----
>  3 files changed, 9 insertions(+), 9 deletions(-)
> 

Reviewed-by: Eric Blake <[e-mail]>

Patch

diff --git a/block/qcow2.h b/block/qcow2.h
index 0fe5f74ed3..42a0058ab7 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -588,7 +588,6 @@  typedef enum QCow2MetadataOverlap {
 
 #define L1E_OFFSET_MASK 0x00fffffffffffe00ULL
 #define L2E_OFFSET_MASK 0x00fffffffffffe00ULL
-#define L2E_COMPRESSED_OFFSET_SIZE_MASK 0x3fffffffffffffffULL
 
 #define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
 
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index bd0597842f..04735ee439 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -556,8 +556,7 @@  static int coroutine_fn do_perform_cow_write(BlockDriverState *bs,
  * offset needs to be aligned to a cluster boundary.
  *
  * If the cluster is unallocated then *host_offset will be 0.
- * If the cluster is compressed then *host_offset will contain the
- * complete compressed cluster descriptor.
+ * If the cluster is compressed then *host_offset will contain the l2 entry.
  *
  * On entry, *bytes is the maximum number of contiguous bytes starting at
  * offset that we are interested in.
@@ -660,7 +659,7 @@  int qcow2_get_host_offset(BlockDriverState *bs, uint64_t offset,
             ret = -EIO;
             goto fail;
         }
-        *host_offset = l2_entry & L2E_COMPRESSED_OFFSET_SIZE_MASK;
+        *host_offset = l2_entry;
         break;
     case QCOW2_SUBCLUSTER_ZERO_PLAIN:
     case QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN:
diff --git a/block/qcow2.c b/block/qcow2.c
index 9727ae8fe3..746ae85b89 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -74,7 +74,7 @@  typedef struct {
 
 static int coroutine_fn
 qcow2_co_preadv_compressed(BlockDriverState *bs,
-                           uint64_t cluster_descriptor,
+                           uint64_t l2_entry,
                            uint64_t offset,
                            uint64_t bytes,
                            QEMUIOVector *qiov,
@@ -2177,7 +2177,7 @@  typedef struct Qcow2AioTask {
 
     BlockDriverState *bs;
     QCow2SubclusterType subcluster_type; /* only for read */
-    uint64_t host_offset; /* or full descriptor in compressed clusters */
+    uint64_t host_offset; /* or l2_entry for compressed read */
     uint64_t offset;
     uint64_t bytes;
     QEMUIOVector *qiov;
@@ -4665,7 +4665,7 @@  qcow2_co_pwritev_compressed_part(BlockDriverState *bs,
 
 static int coroutine_fn
 qcow2_co_preadv_compressed(BlockDriverState *bs,
-                           uint64_t cluster_descriptor,
+                           uint64_t l2_entry,
                            uint64_t offset,
                            uint64_t bytes,
                            QEMUIOVector *qiov,
@@ -4677,8 +4677,10 @@  qcow2_co_preadv_compressed(BlockDriverState *bs,
     uint8_t *buf, *out_buf;
     int offset_in_cluster = offset_into_cluster(s, offset);
 
-    coffset = cluster_descriptor & s->cluster_offset_mask;
-    nb_csectors = ((cluster_descriptor >> s->csize_shift) & s->csize_mask) + 1;
+    assert(qcow2_get_cluster_type(bs, l2_entry) == QCOW2_CLUSTER_COMPRESSED);
+
+    coffset = l2_entry & s->cluster_offset_mask;
+    nb_csectors = ((l2_entry >> s->csize_shift) & s->csize_mask) + 1;
     csize = nb_csectors * QCOW2_COMPRESSED_SECTOR_SIZE -
         (coffset & ~QCOW2_COMPRESSED_SECTOR_MASK);