[v2,2/4] qcow2: Don't round the L1 table allocation up to the sector size

Commit Message

Alberto Garcia Jan. 9, 2020, 7:13 p.m. UTC

The L1 table is read from disk using the byte-based bdrv_pread() and
is never accessed beyond its last element, so there's no need to
allocate more memory than that.

Signed-off-by: Alberto Garcia <[e-mail]>
---
 block/qcow2-cluster.c  | 5 ++---
 block/qcow2-refcount.c | 2 +-
 block/qcow2-snapshot.c | 3 +--
 block/qcow2.c          | 2 +-
 4 files changed, 5 insertions(+), 7 deletions(-)

Comments

Max Reitz Jan. 14, 2020, 1:46 p.m. UTC | #1

On 09.01.20 20:13, Alberto Garcia wrote:
> The L1 table is read from disk using the byte-based bdrv_pread() and
> is never accessed beyond its last element, so there's no need to
> allocate more memory than that.
> 
> Signed-off-by: Alberto Garcia <[e-mail]>
> ---
>  block/qcow2-cluster.c  | 5 ++---
>  block/qcow2-refcount.c | 2 +-
>  block/qcow2-snapshot.c | 3 +--
>  block/qcow2.c          | 2 +-
>  4 files changed, 5 insertions(+), 7 deletions(-)

Reviewed-by: Max Reitz <[e-mail]>

Patch

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 8982b7b762..932fc48919 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -124,12 +124,11 @@  int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t min_size,
 #endif
 
     new_l1_size2 = sizeof(uint64_t) * new_l1_size;
-    new_l1_table = qemu_try_blockalign(bs->file->bs,
-                                       ROUND_UP(new_l1_size2, 512));
+    new_l1_table = qemu_try_blockalign(bs->file->bs, new_l1_size2);
     if (new_l1_table == NULL) {
         return -ENOMEM;
     }
-    memset(new_l1_table, 0, ROUND_UP(new_l1_size2, 512));
+    memset(new_l1_table, 0, new_l1_size2);
 
     if (s->l1_size) {
         memcpy(new_l1_table, s->l1_table, s->l1_size * sizeof(uint64_t));
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index f67ac6b2d8..c963bc8de1 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -1262,7 +1262,7 @@  int qcow2_update_snapshot_refcount(BlockDriverState *bs,
      * l1_table_offset when it is the current s->l1_table_offset! Be careful
      * when changing this! */
     if (l1_table_offset != s->l1_table_offset) {
-        l1_table = g_try_malloc0(ROUND_UP(l1_size2, 512));
+        l1_table = g_try_malloc0(l1_size2);
         if (l1_size2 && l1_table == NULL) {
             ret = -ENOMEM;
             goto fail;
diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 5ab64da1ec..82c32d4c9b 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -1024,8 +1024,7 @@  int qcow2_snapshot_load_tmp(BlockDriverState *bs,
         return ret;
     }
     new_l1_bytes = sn->l1_size * sizeof(uint64_t);
-    new_l1_table = qemu_try_blockalign(bs->file->bs,
-                                       ROUND_UP(new_l1_bytes, 512));
+    new_l1_table = qemu_try_blockalign(bs->file->bs, new_l1_bytes);
     if (new_l1_table == NULL) {
         return -ENOMEM;
     }
diff --git a/block/qcow2.c b/block/qcow2.c
index 87ca2832f0..848a6c5182 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1499,7 +1499,7 @@  static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
 
     if (s->l1_size > 0) {
         s->l1_table = qemu_try_blockalign(bs->file->bs,
-            ROUND_UP(s->l1_size * sizeof(uint64_t), 512));
+                                          s->l1_size * sizeof(uint64_t));
         if (s->l1_table == NULL) {
             error_setg(errp, "Could not allocate L1 table");
             ret = -ENOMEM;