[Qemu-stable] [PATCH v2] snapshot: use local variable to bdrv_pwrite_sync L1 table

[Zhang Haoyu]

Use local variable to bdrv_pwrite_sync L1 table,
needless to make conversion of cached L1 table between
big-endian and host style.

Signed-off-by: Zhang Haoyu <address@hidden>
---
v1 -> v2:
 - remove the superflous assignment, l1_table = NULL;
 - replace 512 with BDRV_SECTOR_SIZE, and align_offset with ROUND_UP
 - remove needless check of if (l1_table) before g_free(l1_table)

 block/qcow2-refcount.c | 24 +++++++-----------------
 1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 2bcaaf9..29a916a 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -881,14 +881,17 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
 {
     BDRVQcowState *s = bs->opaque;
     uint64_t *l1_table, *l2_table, l2_offset, offset, l1_size2;
-    bool l1_allocated = false;
     int64_t old_offset, old_l2_offset;
     int i, j, l1_modified = 0, nb_csectors, refcount;
     int ret;
 
     l2_table = NULL;
-    l1_table = NULL;
     l1_size2 = l1_size * sizeof(uint64_t);
+    l1_table = g_try_malloc0(ROUND_UP(l1_size2, BDRV_SECTOR_SIZE));
+    if (l1_size2 && l1_table == NULL) {
+        ret = -ENOMEM;
+        goto fail;
+    }
 
     s->cache_discards = true;
 
@@ -896,13 +899,6 @@ 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(align_offset(l1_size2, 512));
-        if (l1_size2 && l1_table == NULL) {
-            ret = -ENOMEM;
-            goto fail;
-        }
-        l1_allocated = true;
-
         ret = bdrv_pread(bs->file, l1_table_offset, l1_table, l1_size2);
         if (ret < 0) {
             goto fail;
@@ -912,8 +908,7 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
             be64_to_cpus(&l1_table[i]);
     } else {
         assert(l1_size == s->l1_size);
-        l1_table = s->l1_table;
-        l1_allocated = false;
+        memcpy(l1_table, s->l1_table, l1_size2);
     }
 
     for(i = 0; i < l1_size; i++) {
@@ -1055,13 +1050,8 @@ fail:
         }
 
         ret = bdrv_pwrite_sync(bs->file, l1_table_offset, l1_table, l1_size2);
-
-        for (i = 0; i < l1_size; i++) {
-            be64_to_cpus(&l1_table[i]);
-        }
     }
-    if (l1_allocated)
-        g_free(l1_table);
+    g_free(l1_table);
     return ret;
 }
 
-- 
1.7.12.4