Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches

# gpg: Signature made Tue 18 Jul 2017 14:29:59 BST
# gpg:                using RSA key 0x7F09B272C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (21 commits)
  qemu-img: Check for backing image if specified during create
  blockdev: move BDRV_O_NO_BACKING option forward
  block/vvfat: Fix compiler warning with gcc 7
  vvfat: initialize memory after allocating it
  vvfat: correctly parse non-ASCII short and long file names
  vvfat: add a constant for bootsector name
  vvfat: add constants for special values of name[0]
  qemu-iotests: Test unplug of -device without drive
  qemu-iotests: Test 'info block'
  scsi-disk: bdrv_attach_dev() for empty CD-ROM
  ide: bdrv_attach_dev() for empty CD-ROM
  block: List anonymous device BBs in query-block
  block/qapi: Use blk_all_next() for query-block
  block: Make blk_all_next() public
  block/qapi: Add qdev device name to query-block
  block: Make blk_get_attached_dev_id() public
  block/vpc.c: Handle write failures in get_image_offset()
  block/vmdk: Report failures in vmdk_read_cid()
  block: remove timer canceling in throttle_config()
  block: add clock_type field to ThrottleGroup
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 52 insertions, 42 deletions

diff --git a/block.c b/block.c
index 98a9209371..2dd9262cd0 100644
--- a/block.c
+++ b/block.c
@@ -4396,55 +4396,65 @@ void bdrv_img_create(const char *filename, const char *fmt,
 
     backing_fmt = qemu_opt_get(opts, BLOCK_OPT_BACKING_FMT);
 
-    // The size for the image must always be specified, with one exception:
-    // If we are using a backing file, we can obtain the size from there
+    /* The size for the image must always be specified, unless we have a backing
+     * file and we have not been forbidden from opening it. */
     size = qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 0);
-    if (size == -1) {
-        if (backing_file) {
-            BlockDriverState *bs;
-            char *full_backing = g_new0(char, PATH_MAX);
-            int64_t size;
-            int back_flags;
-            QDict *backing_options = NULL;
-
-            bdrv_get_full_backing_filename_from_filename(filename, backing_file,
-                                                         full_backing, PATH_MAX,
-                                                         &local_err);
-            if (local_err) {
-                g_free(full_backing);
-                goto out;
-            }
+    if (backing_file && !(flags & BDRV_O_NO_BACKING)) {
+        BlockDriverState *bs;
+        char *full_backing = g_new0(char, PATH_MAX);
+        int back_flags;
+        QDict *backing_options = NULL;
+
+        bdrv_get_full_backing_filename_from_filename(filename, backing_file,
+                                                     full_backing, PATH_MAX,
+                                                     &local_err);
+        if (local_err) {
+            g_free(full_backing);
+            goto out;
+        }
 
-            /* backing files always opened read-only */
-            back_flags = flags;
-            back_flags &= ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
+        /* backing files always opened read-only */
+        back_flags = flags;
+        back_flags &= ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
 
-            if (backing_fmt) {
-                backing_options = qdict_new();
-                qdict_put_str(backing_options, "driver", backing_fmt);
-            }
+        if (backing_fmt) {
+            backing_options = qdict_new();
+            qdict_put_str(backing_options, "driver", backing_fmt);
+        }
 
-            bs = bdrv_open(full_backing, NULL, backing_options, back_flags,
-                           &local_err);
-            g_free(full_backing);
-            if (!bs) {
-                goto out;
-            }
-            size = bdrv_getlength(bs);
-            if (size < 0) {
-                error_setg_errno(errp, -size, "Could not get size of '%s'",
-                                 backing_file);
-                bdrv_unref(bs);
-                goto out;
+        bs = bdrv_open(full_backing, NULL, backing_options, back_flags,
+                       &local_err);
+        g_free(full_backing);
+        if (!bs && size != -1) {
+            /* Couldn't open BS, but we have a size, so it's nonfatal */
+            warn_reportf_err(local_err,
+                            "Could not verify backing image. "
+                            "This may become an error in future versions.\n");
+            local_err = NULL;
+        } else if (!bs) {
+            /* Couldn't open bs, do not have size */
+            error_append_hint(&local_err,
+                              "Could not open backing image to determine size.\n");
+            goto out;
+        } else {
+            if (size == -1) {
+                /* Opened BS, have no size */
+                size = bdrv_getlength(bs);
+                if (size < 0) {
+                    error_setg_errno(errp, -size, "Could not get size of '%s'",
+                                     backing_file);
+                    bdrv_unref(bs);
+                    goto out;
+                }
+                qemu_opt_set_number(opts, BLOCK_OPT_SIZE, size, &error_abort);
             }
-
-            qemu_opt_set_number(opts, BLOCK_OPT_SIZE, size, &error_abort);
-
             bdrv_unref(bs);
-        } else {
-            error_setg(errp, "Image creation needs a size parameter");
-            goto out;
         }
+    } /* (backing_file && !(flags & BDRV_O_NO_BACKING)) */
+
+    if (size == -1) {
+        error_setg(errp, "Image creation needs a size parameter");
+        goto out;
     }
 
     if (!quiet) {