On Mon, Jul 31, 2017 at 11:54:57AM -0300, Philippe Mathieu-Daudé wrote:
> On 07/31/2017 11:38 AM, Jeff Cody wrote:
> >On Mon, Jul 31, 2017 at 02:51:11PM +0200, Kevin Wolf wrote:
> >>When skipping implicit nodes in bdrv_block_device_info(), we know that
> >>bs0 is always non-NULL; initially, because it's taken from a BdrvChild
> >
> >Not to mention, we deference bs0 in the chunk of code right above this, so
> >we'd segfault anyway if the initial value was NULL.
>
> Yes, please move your assert before:
>
> 137: if (bs0->drv && bs0->backing) {
>
> Once there:
> Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>
>
I don't think moving the assert() is the correct thing to do, as it is
useful when iterating in the while() via backing_bs().
But maybe adding some asserts would be useful, if we are really concerned.
Looking at the code:
135 }
136
Maybe add an assert(bs0) here, as you suggest...
137 if (bs0->drv && bs0->backing) {
138 info->backing_file_depth++;
139 bs0 = bs0->backing->bs;
But then maybe we want one here, too? Or maybe that is overkill :)
140 (*p_image_info)->has_backing_image = true;
141 p_image_info = &((*p_image_info)->backing_image);
142 } else {
143 break;
144 }
145
146 /* Skip automatically inserted nodes that the user isn't aware of
for
147 * query-block (blk != NULL), but not for query-named-block-nodes */
148 while (blk && bs0 && bs0->drv && bs0->implicit) {
149 bs0 = backing_bs(bs0);
150 }
> >
> >>and a BdrvChild never has a NULL bs, and after the first iteration
> >>because implicit nodes always have a backing file.
> >>
> >>Remove the NULL check and add an assertion that the implicit node does
> >>indeed have a backing file.
> >>
> >>Signed-off-by: Kevin Wolf <kw...@redhat.com>
> >
> >
> >Reviewed-by: Jeff Cody <jc...@redhat.com>
> >
> >
> >
> >>---
> >> block/qapi.c | 3 ++-
> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/block/qapi.c b/block/qapi.c
> >>index d2b18ee9df..5f1a71f5d2 100644
> >>--- a/block/qapi.c
> >>+++ b/block/qapi.c
> >>@@ -145,8 +145,9 @@ BlockDeviceInfo *bdrv_block_device_info(BlockBackend
> >>*blk,
> >> /* Skip automatically inserted nodes that the user isn't aware of
> >> for
> >> * query-block (blk != NULL), but not for query-named-block-nodes
> >> */
> >>- while (blk && bs0 && bs0->drv && bs0->implicit) {
> >>+ while (blk && bs0->drv && bs0->implicit) {
> >> bs0 = backing_bs(bs0);
> >>+ assert(bs0);
> >> }
> >> }
> >>--
> >>2.13.3
> >>
> >>
> >
