[v5,30/31] qcow2: Add subcluster support to qcow2_measure()

Commit Message

Alberto Garcia May 5, 2020, 5:38 p.m. UTC

Extended L2 entries are bigger than normal L2 entries so this has an
impact on the amount of metadata needed for a qcow2 file.

Signed-off-by: Alberto Garcia <[e-mail]>
Reviewed-by: Max Reitz <[e-mail]>
---
 block/qcow2.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

Comments

Eric Blake May 6, 2020, 6:13 p.m. UTC | #1

On 5/5/20 12:38 PM, Alberto Garcia wrote:
> Extended L2 entries are bigger than normal L2 entries so this has an
> impact on the amount of metadata needed for a qcow2 file.
> 
> Signed-off-by: Alberto Garcia <[e-mail]>
> Reviewed-by: Max Reitz <[e-mail]>
> ---
>   block/qcow2.c | 19 ++++++++++++-------
>   1 file changed, 12 insertions(+), 7 deletions(-)

Should this be hoisted earlier in the series, before 28/31?

Should there be iotest coverage?

Alberto Garcia May 7, 2020, 3:16 p.m. UTC | #2

On Wed 06 May 2020 08:13:51 PM CEST, Eric Blake wrote:
> On 5/5/20 12:38 PM, Alberto Garcia wrote:
>> Extended L2 entries are bigger than normal L2 entries so this has an
>> impact on the amount of metadata needed for a qcow2 file.
>> 
>> Signed-off-by: Alberto Garcia <[e-mail]>
>> Reviewed-by: Max Reitz <[e-mail]>
>> ---
>>   block/qcow2.c | 19 ++++++++++++-------
>>   1 file changed, 12 insertions(+), 7 deletions(-)
>
> Should this be hoisted earlier in the series, before 28/31?

I can do that if I call qcow2_calc_prealloc_size() with extended_l2
always set to false (because there would be no BLOCK_OPT_EXTL2 that the
caller could use). Maybe it's not a bad idea.

> Should there be iotest coverage?

There are already, in the last patch.

Berto

Patch

diff --git a/block/qcow2.c b/block/qcow2.c
index 18c8e3f52a..31d72f1297 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3173,28 +3173,31 @@  int64_t qcow2_refcount_metadata_size(int64_t clusters, size_t cluster_size,
  * @total_size: virtual disk size in bytes
  * @cluster_size: cluster size in bytes
  * @refcount_order: refcount bits power-of-2 exponent
+ * @extended_l2: true if the image has extended L2 entries
  *
  * Returns: Total number of bytes required for the fully allocated image
  * (including metadata).
  */
 static int64_t qcow2_calc_prealloc_size(int64_t total_size,
                                         size_t cluster_size,
-                                        int refcount_order)
+                                        int refcount_order,
+                                        bool extended_l2)
 {
     int64_t meta_size = 0;
     uint64_t nl1e, nl2e;
     int64_t aligned_total_size = ROUND_UP(total_size, cluster_size);
+    size_t l2e_size = extended_l2 ? L2E_SIZE_EXTENDED : L2E_SIZE_NORMAL;
 
     /* header: 1 cluster */
     meta_size += cluster_size;
 
     /* total size of L2 tables */
     nl2e = aligned_total_size / cluster_size;
-    nl2e = ROUND_UP(nl2e, cluster_size / sizeof(uint64_t));
-    meta_size += nl2e * sizeof(uint64_t);
+    nl2e = ROUND_UP(nl2e, cluster_size / l2e_size);
+    meta_size += nl2e * l2e_size;
 
     /* total size of L1 tables */
-    nl1e = nl2e * sizeof(uint64_t) / cluster_size;
+    nl1e = nl2e * l2e_size / cluster_size;
     nl1e = ROUND_UP(nl1e, cluster_size / sizeof(uint64_t));
     meta_size += nl1e * sizeof(uint64_t);
 
@@ -4765,6 +4768,7 @@  static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
     bool has_backing_file;
     bool has_luks;
     bool extended_l2;
+    size_t l2e_size;
 
     /* Parse image creation options */
     extended_l2 = qemu_opt_get_bool_del(opts, BLOCK_OPT_EXTL2, false);
@@ -4833,8 +4837,9 @@  static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
     virtual_size = ROUND_UP(virtual_size, cluster_size);
 
     /* Check that virtual disk size is valid */
+    l2e_size = extended_l2 ? L2E_SIZE_EXTENDED : L2E_SIZE_NORMAL;
     l2_tables = DIV_ROUND_UP(virtual_size / cluster_size,
-                             cluster_size / sizeof(uint64_t));
+                             cluster_size / l2e_size);
     if (l2_tables * sizeof(uint64_t) > QCOW_MAX_L1_SIZE) {
         error_setg(&local_err, "The image size is too large "
                                "(try using a larger cluster size)");
@@ -4897,9 +4902,9 @@  static BlockMeasureInfo *qcow2_measure(QemuOpts *opts, BlockDriverState *in_bs,
     }
 
     info = g_new(BlockMeasureInfo, 1);
-    info->fully_allocated =
+    info->fully_allocated = luks_payload_size +
         qcow2_calc_prealloc_size(virtual_size, cluster_size,
-                                 ctz32(refcount_bits)) + luks_payload_size;
+                                 ctz32(refcount_bits), extended_l2);
 
     /* Remove data clusters that are not required.  This overestimates the
      * required size because metadata needed for the fully allocated file is