On 2/4/20 11:08 AM, Max Reitz wrote:
After the series this patch belongs to, we want to have a common
BdrvChildClass that encompasses all of child_file, child_format, and
child_backing. Such a single class needs a single .inherit_options()
implementation, and this patch introduces it.
The next patch will show how the existing implementations can fall back
to it just by passing appropriate BdrvChildRole and parent_is_format
values.
Signed-off-by: Max Reitz <mre...@redhat.com>
---
block.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 84 insertions(+)
No impact until the next patch, but the division of patches was wise.
+ /*
+ * First, decide whether to set, clear, or leave BDRV_O_PROTOCOL.
+ * Generally, the question to answer is: Should this child be
+ * format-probed by default?
+ */
+
+ /*
+ * Pure and non-filtered data children of non-format nodes should
+ * be probed by default (even when the node itself has BDRV_O_PROTOCOL
+ * set). This only affects a very limited set of drivers (namely
+ * quorum and blkverify when this comment was written).
+ * Force-clear BDRV_O_PROTOCOL then.
+ */
+ if (!parent_is_format &&
+ (role & (BDRV_CHILD_DATA | BDRV_CHILD_METADATA |
+ BDRV_CHILD_FILTERED)) ==
+ BDRV_CHILD_DATA)
+ {
+ flags &= ~BDRV_O_PROTOCOL;
+ }
+
+ /*
+ * All children of format nodes (except for COW children) and all
+ * metadata children in general should never be format-probed.
+ * Force-set BDRV_O_PROTOCOL then.
+ */
+ if ((parent_is_format && !(role & BDRV_CHILD_COW)) ||
+ (role & BDRV_CHILD_METADATA))
Should this use 'else if', to make it obvious that we never have a path
that both force-clears and force-sets BDRV_O_PROTOCOL? But a careful
reading shows that the two 'if' are mutually exclusive, even without the
second using 'else if'.
+ {
+ flags |= BDRV_O_PROTOCOL;
+ }
+
Looks good! Lots of decision trees, but also lots of good comments
backing up that complexity.
Reviewed-by: Eric Blake <ebl...@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
