From 62a30a970548466900ac45962a0fe8c051514329 Mon Sep 17 00:00:00 2001

From: Max Reitz <mreitz@redhat.com>

Date: Tue, 3 Dec 2013 14:57:52 +0100

Subject: [PATCH] block: Close backing file early in bdrv_img_create

Leaving the backing file open although it is not needed anymore can

cause problems if it is opened through a block driver which allows

exclusive access only and if the create function of the block driver

used for the top image (the one being created) tries to close and reopen

the image file (which will include opening the backing file a second

time).

In particular, this will happen with a backing file opened through

qemu-nbd and using qcow2 as the top image file format (which reopens the

image to flush it to disk).

In addition, the BlockDriverState in bdrv_img_create() is used for the

backing file only; it should therefore be made local to the respective

block.

Signed-off-by: Max Reitz <mreitz@redhat.com>

---

 block.c | 8 ++++----

 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/block.c b/block.c

index 382ea71..0468765 100644

--- a/block.c

+++ b/block.c

@@ -4504,7 +4504,6 @@ void bdrv_img_create(const char *filename, const char *fmt,

 {

     QEMUOptionParameter *param = NULL, *create_options = NULL;

     QEMUOptionParameter *backing_fmt, *backing_file, *size;

-    BlockDriverState *bs = NULL;

     BlockDriver *drv, *proto_drv;

     BlockDriver *backing_drv = NULL;

     Error *local_err = NULL;

@@ -4583,6 +4582,7 @@ void bdrv_img_create(const char *filename, const char *fmt,

     size = get_option_parameter(param, BLOCK_OPT_SIZE);

     if (size && size->value.n == -1) {

         if (backing_file && backing_file->value.s) {

+            BlockDriverState *bs;

             uint64_t size;

             char buf[32];

             int back_flags;

@@ -4601,6 +4601,7 @@ void bdrv_img_create(const char *filename, const char *fmt,

                                  error_get_pretty(local_err));

                 error_free(local_err);

                 local_err = NULL;

+                bdrv_unref(bs);

                 goto out;

             }

             bdrv_get_geometry(bs, &size);

@@ -4608,6 +4609,8 @@ void bdrv_img_create(const char *filename, const char *fmt,

             snprintf(buf, sizeof(buf), "%" PRId64, size);

             set_option_parameter(param, BLOCK_OPT_SIZE, buf);

+

+            bdrv_unref(bs);

         } else {

             error_setg(errp, "Image creation needs a size parameter");

             goto out;

@@ -4638,9 +4641,6 @@ out:

     free_option_parameters(create_options);

     free_option_parameters(param);

-    if (bs) {

-        bdrv_unref(bs);

-    }

     if (error_is_set(&local_err)) {

         error_propagate(errp, local_err);

     }