From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40075) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dSpb5-00043k-6N for qemu-devel@nongnu.org; Wed, 05 Jul 2017 15:04:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dSpb4-0005wN-76 for qemu-devel@nongnu.org; Wed, 05 Jul 2017 15:04:23 -0400 From: Max Reitz Date: Wed, 5 Jul 2017 21:04:02 +0200 Message-Id: <20170705190404.22449-4-mreitz@redhat.com> In-Reply-To: <20170705190404.22449-1-mreitz@redhat.com> References: <20170705190404.22449-1-mreitz@redhat.com> Subject: [Qemu-devel] [PATCH v4 3/5] block: qobject_is_equal() in bdrv_reopen_prepare() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Max Reitz , Kevin Wolf , Eric Blake , Markus Armbruster Currently, bdrv_reopen_prepare() assumes that all BDS options are strings. However, this is not the case if the BDS has been created through the json: pseudo-protocol or blockdev-add. Note that the user-invokable reopen command is an HMP command, so you can only specify strings there. Therefore, specifying a non-string option with the "same" value as it was when originally created will now return an error because the values are supposedly similar (and there is no way for the user to circumvent this but to just not specify the option again -- however, this is still strictly better than just crashing). Signed-off-by: Max Reitz --- block.c | 29 ++++++++++++++++++----------- 1 file changed, 18 insertions(+), 11 deletions(-) diff --git a/block.c b/block.c index 913bb43..f8c8e92 100644 --- a/block.c +++ b/block.c @@ -2947,19 +2947,26 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, const QDictEntry *entry = qdict_first(reopen_state->options); do { - QString *new_obj = qobject_to_qstring(entry->value); - const char *new = qstring_get_str(new_obj); + QObject *new = entry->value; + QObject *old = qdict_get(reopen_state->bs->options, entry->key); + /* - * Caution: while qdict_get_try_str() is fine, getting - * non-string types would require more care. When - * bs->options come from -blockdev or blockdev_add, its - * members are typed according to the QAPI schema, but - * when they come from -drive, they're all QString. + * TODO: When using -drive to specify blockdev options, all values + * will be strings; however, when using -blockdev, blockdev-add or + * filenames using the json:{} pseudo-protocol, they will be + * correctly typed. + * In contrast, reopening options are (currently) always strings + * (because you can only specify them through qemu-io; all other + * callers do not specify any options). + * Therefore, when using anything other than -drive to create a BDS, + * this cannot detect non-string options as unchanged, because + * qobject_is_equal() always returns false for objects of different + * type. In the future, this should be remedied by correctly typing + * all options. For now, this is not too big of an issue because + * the user can simply omit options which cannot be changed anyway, + * so they will stay unchanged. */ - const char *old = qdict_get_try_str(reopen_state->bs->options, - entry->key); - - if (!old || strcmp(new, old)) { + if (!qobject_is_equal(new, old)) { error_setg(errp, "Cannot change the option '%s'", entry->key); ret = -EINVAL; goto error; -- 2.9.4