Ask for read-write permissions when opening files

Found some places that seems needs this explicitly, now that
read-write is not the default.

Signed-off-by: Naphtali Sprei <nsprei@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

block/qcow2.c

@@ -998,7 +998,7 @@ exit:
     if (prealloc) {
         BlockDriverState *bs;
         bs = bdrv_new("");
-        bdrv_open(bs, filename, BDRV_O_CACHE_WB);
+        bdrv_open(bs, filename, BDRV_O_CACHE_WB | BDRV_O_RDWR);
         preallocate(bs);
         bdrv_close(bs);
     }

block/vvfat.c

@@ -2792,7 +2792,7 @@ static int enable_write_target(BDRVVVFATState *s)
     if (bdrv_create(bdrv_qcow, s->qcow_filename, options) < 0)
 	return -1;
     s->qcow = bdrv_new("");
-    if (s->qcow == NULL || bdrv_open(s->qcow, s->qcow_filename, 0) < 0)
+    if (s->qcow == NULL || bdrv_open(s->qcow, s->qcow_filename, BDRV_O_RDWR) < 0)
 	return -1;
 
 #ifndef _WIN32

qemu-img.c

@@ -1116,7 +1116,7 @@ static int img_rebase(int argc, char **argv)
     if (!bs)
         error("Not enough memory");
 
-    flags = BRDV_O_FLAGS | (unsafe ? BDRV_O_NO_BACKING : 0);
+    flags = BRDV_O_FLAGS | BDRV_O_RDWR | (unsafe ? BDRV_O_NO_BACKING : 0);
     if (bdrv_open2(bs, filename, flags, NULL) < 0) {
         error("Could not open '%s'", filename);
     }
@@ -1157,7 +1157,7 @@ static int img_rebase(int argc, char **argv)
         }
 
         bs_new_backing = bdrv_new("new_backing");
-        if (bdrv_open2(bs_new_backing, out_baseimg, BRDV_O_FLAGS,
+        if (bdrv_open2(bs_new_backing, out_baseimg, BRDV_O_FLAGS | BDRV_O_RDWR,
             new_backing_drv))
         {
             error("Could not open new backing file '%s'", backing_name);