From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:39003) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gk9gn-0001s4-9a for qemu-devel@nongnu.org; Thu, 17 Jan 2019 10:34:45 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gk9gh-0007bk-Kj for qemu-devel@nongnu.org; Thu, 17 Jan 2019 10:34:41 -0500 From: Alberto Garcia Date: Thu, 17 Jan 2019 17:33:58 +0200 Message-Id: <6ec504767392cb91591542c416f0c2ae52f847f8.1547739122.git.berto@igalia.com> In-Reply-To: References: In-Reply-To: References: Subject: [Qemu-devel] [PATCH 07/13] block: Allow omitting the 'backing' option in certain cases List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Alberto Garcia , qemu-block@nongnu.org, Kevin Wolf , Max Reitz Of all options of type BlockdevRef used to specify children in BlockdevOptions, 'backing' is the only one that is optional. For "x-blockdev-reopen" we want that if an option is omitted then it must be reset to its default value. The default value of 'backing' means that QEMU opens the backing file specified in the image metadata, but this is not something that we want to support for the reopen operation. Because of this the 'backing' option has to be specified during reopen, pointing to the existing backing file if we want to keep it, or pointing to a different one (or NULL) if we want to replace it (to be implemented in a subsequent patch). In order to simplify things a bit and not to require that the user passes the 'backing' option to every single block device even when it's clearly not necessary, this patch allows omitting this option if the block device being reopened doesn't have a backing file attached _and_ no default backing file is specified in the image metadata. Signed-off-by: Alberto Garcia --- block.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index fd51f1cd35..897c8b85cd 100644 --- a/block.c +++ b/block.c @@ -3336,7 +3336,13 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, drv_prepared = true; - if (reopen_state->backing_missing) { + /* + * We must provide the 'backing' option if the BDS has a backing + * file or if the image file has a backing file name as part of + * its metadata. Otherwise the 'backing' option can be omitted. + */ + if (reopen_state->backing_missing && + (backing_bs(reopen_state->bs) || reopen_state->bs->backing_file[0])) { error_setg(errp, "backing is missing for '%s'", reopen_state->bs->node_name); ret = -EINVAL; -- 2.11.0