On Fri, Apr 18, 2014 at 03:44:19PM +0200, Benoît Canet wrote:
> From: Kevin Wolf <kw...@redhat.com>
>
> If you open an image temporarily just because you want to check its size
> or get it flushed, there's no real reason to open the whole backing file
> chain.
>
> This is a backport of c9fbb99d41b05acf0d7b93deb2fcdbf9047c238e to
> qemu 1.7.1.
>
> The backport was done to fix a bug where QEMU 1.7.1 would crash or freeze
> when the user take around 80 consecutives snapshots in a row.
>
> git bisect would lead to commit: ba2ab2f2ca4150a7e314fbb19fa158bd8ddc36eb
> and it was clear that BDRV_NO_BACKING was missing.
>
> Signed-off-by: Kevin Wolf <kw...@redhat.com>
> Signed-off-by: Benoit Canet <ben...@irqsave.net>
> ---
> block.c | 4 ++--
> block/qcow2.c | 3 ++-
> block/vmdk.c | 2 +-
> 3 files changed, 5 insertions(+), 4 deletions(-)
CCed qemu-devel@nongnu.org and Mike Roth, who maintains the stable tree.
This patch should go directly into stable through Mike. It's already in
master so Kevin and I are not involved.
> diff --git a/block.c b/block.c
> index 382ea71..9f638ea 100644
> --- a/block.c
> +++ b/block.c
> @@ -1064,9 +1064,9 @@ int bdrv_open(BlockDriverState *bs, const char
> *filename, QDict *options,
> /* if snapshot, we create a temporary backing file and open it
> instead of opening 'filename' directly */
>
> - /* if there is a backing file, use it */
> bs1 = bdrv_new("");
> - ret = bdrv_open(bs1, filename, NULL, 0, drv, &local_err);
> + ret = bdrv_open(bs1, filename, NULL, BDRV_O_NO_BACKING, drv,
> + &local_err);
> if (ret < 0) {
> bdrv_unref(bs1);
> goto fail;
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 6e5d98d..344c63e 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -1588,7 +1588,8 @@ static int qcow2_create2(const char *filename, int64_t
> total_size,
>
> /* Reopen the image without BDRV_O_NO_FLUSH to flush it before returning
> */
> ret = bdrv_open(bs, filename, NULL,
> - BDRV_O_RDWR | BDRV_O_CACHE_WB, drv, &local_err);
> + BDRV_O_RDWR | BDRV_O_CACHE_WB | BDRV_O_NO_BACKING,
> + drv, &local_err);
> if (error_is_set(&local_err)) {
> error_propagate(errp, local_err);
> goto out;
> diff --git a/block/vmdk.c b/block/vmdk.c
> index a7ebd0f..d35a9d7 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -1689,7 +1689,7 @@ static int vmdk_create(const char *filename,
> QEMUOptionParameter *options,
> }
> if (backing_file) {
> BlockDriverState *bs = bdrv_new("");
> - ret = bdrv_open(bs, backing_file, NULL, 0, NULL, errp);
> + ret = bdrv_open(bs, backing_file, NULL, BDRV_O_NO_BACKING, NULL,
> errp);
> if (ret != 0) {
> bdrv_unref(bs);
> return ret;
> --
> 1.7.10.4
>
