[Qemu-devel] [PATCH for-2.6 1/7] block/vpc: fix VPC 'qemu-img create' regression

[Jeff Cody <jcody@redhat.com>]

Commit 'b8f45cdf7827e39f9a1e6cc446f5972cc6144237' switched VPC
over to using blk_pwrite() instead of bdrv_pwrite_sync().  The
return value of bdrv_pwrite_sync() was always 0 for success, and
create_dynamic_disk() in one instance checked for a non-zero return
value to indicate error.  However, blk_pwrite() may return positive
values for success.

This fails silently as well, since vpc_create() did not set errp
in this failuer case.  Set errp in all instances in vpc_create().

Signed-off-by: Jeff Cody <jcody@redhat.com>
---
 block/vpc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/vpc.c b/block/vpc.c
index 8435205..bc3d1c6 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -774,7 +774,7 @@ static int create_dynamic_disk(BlockBackend *blk, uint8_t *buf,
     num_bat_entries = (total_sectors + block_size / 512) / (block_size / 512);
 
     ret = blk_pwrite(blk, offset, buf, HEADER_SIZE);
-    if (ret) {
+    if (ret < 0) {
         goto fail;
     }
 
@@ -873,6 +873,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
         } else if (!strcmp(disk_type_param, "fixed")) {
             disk_type = VHD_FIXED;
         } else {
+            error_setg(errp, "Invalid disk type, %s", disk_type_param);
             ret = -EINVAL;
             goto out;
         }
@@ -924,6 +925,7 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
         total_sectors = total_size / BDRV_SECTOR_SIZE;
         /* Allow a maximum disk size of approximately 2 TB */
         if (total_sectors > VHD_MAX_SECTORS) {
+            error_setg(errp, "Disk size is too large, max size is 2040 GiB");
             ret = -EFBIG;
             goto out;
         }
@@ -974,6 +976,9 @@ static int vpc_create(const char *filename, QemuOpts *opts, Error **errp)
     } else {
         ret = create_fixed_disk(blk, buf, total_size);
     }
+    if (ret < 0) {
+        error_setg(errp, "Unable to create or write VHD header");
+    }
 
 out:
     blk_unref(blk);
-- 
1.9.3