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

2021-05-04 Thread Eric Blake
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 
> ---
>  block/qcow2.h |  1 -
>  block/qcow2-cluster.c |  5 ++---
>  block/qcow2.c | 12 +++-
>  3 files changed, 9 insertions(+), 9 deletions(-)
> 

Reviewed-by: Eric Blake 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.   +1-919-301-3226
Virtualization:  qemu.org | libvirt.org




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

2021-05-04 Thread Vladimir Sementsov-Ogievskiy
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 
---
 block/qcow2.h |  1 -
 block/qcow2-cluster.c |  5 ++---
 block/qcow2.c | 12 +++-
 3 files changed, 9 insertions(+), 9 deletions(-)

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 0x00fffe00ULL
 #define L2E_OFFSET_MASK 0x00fffe00ULL
-#define L2E_COMPRESSED_OFFSET_SIZE_MASK 0x3fffULL
 
 #define REFT_OFFSET_MASK 0xfe00ULL
 
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);
 
-- 
2.29.2