From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59563) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ePkzN-0007Dv-6P for qemu-devel@nongnu.org; Fri, 15 Dec 2017 03:05:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ePkzJ-0001IN-EU for qemu-devel@nongnu.org; Fri, 15 Dec 2017 03:05:01 -0500 From: Fam Zheng Date: Fri, 15 Dec 2017 16:04:45 +0800 Message-Id: <20171215080446.10671-2-famz@redhat.com> In-Reply-To: <20171215080446.10671-1-famz@redhat.com> References: <20171215080446.10671-1-famz@redhat.com> Subject: [Qemu-devel] [PATCH 1/2] block: Open backing image in force share mode for size probe List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Kevin Wolf , Max Reitz , qemu-block@nongnu.org Management tools create overlays of running guests with qemu-img: $ qemu-img create -b /image/in/use.qcow2 -f qcow2 /overlay/image.qcow2 but this doesn't work anymore due to image locking: qemu-img: /overlay/image.qcow2: Failed to get shared "write" lock Is another process using the image? Could not open backing image to determine size. Use the force share option to allow this use case again. Cc: qemu-stable@nongnu.org Signed-off-by: Fam Zheng --- block.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index 9a1a0d1e73..f236431da1 100644 --- a/block.c +++ b/block.c @@ -4593,10 +4593,11 @@ void bdrv_img_create(const char *filename, const char *fmt, back_flags = flags; back_flags &= ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING); + backing_options = qdict_new(); if (backing_fmt) { - backing_options = qdict_new(); qdict_put_str(backing_options, "driver", backing_fmt); } + qdict_put_bool(backing_options, BDRV_OPT_FORCE_SHARE, true); bs = bdrv_open(full_backing, NULL, backing_options, back_flags, &local_err); -- 2.14.3