[Qemu-block] [PATCH v3 5/6] vmdk: Set maximum bytes allocated in one cycle

[Ashijeet Acharya]

Set the maximum bytes allowed to get allocated at once to be not more
than the extent size boundary to handle writes at two separate extents
appropriately.

Signed-off-by: Ashijeet Acharya <address@hidden>
---
 block/vmdk.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/block/vmdk.c b/block/vmdk.c
index a8babd7..9456ddd 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1767,6 +1767,7 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t 
offset,
     int64_t offset_in_cluster, n_bytes;
     uint64_t cluster_offset;
     uint64_t bytes_done = 0;
+    uint64_t extent_size;
     VmdkMetaData m_data;
     uint32_t total_alloc_clusters = 0;
 
@@ -1782,9 +1783,17 @@ static int vmdk_pwritev(BlockDriverState *bs, uint64_t 
offset,
         if (!extent) {
             return -EIO;
         }
+        extent_size = extent->end_sector * BDRV_SECTOR_SIZE;
+
         offset_in_cluster = vmdk_find_offset_in_cluster(extent, offset);
-        n_bytes = MIN(bytes, extent->cluster_sectors * BDRV_SECTOR_SIZE
-                             - offset_in_cluster);
+
+        /* truncate n_bytes to first cluster because we need to perform COW */
+        if (offset_in_cluster > 0) {
+            n_bytes = MIN(bytes, extent->cluster_sectors * BDRV_SECTOR_SIZE
+                                 - offset_in_cluster);
+        } else {
+            n_bytes = MIN(bytes, extent_size - offset);
+        }
 
         ret = vmdk_alloc_cluster_offset(bs, extent, &m_data, offset,
                                         !(extent->compressed || zeroed),
-- 
2.6.2