On 5/13/20 6:05 AM, Max Reitz wrote:
Let child_file's, child_format's, and child_backing's .inherit_options()
implementations fall back to bdrv_inherited_options() to show that it
would really work for all of these cases, if only the parents passed the
appropriate BdrvChildRole and parent_is_format values.
(Also, make bdrv_open_inherit(), the only place to explicitly call
bdrv_backing_options(), call bdrv_inherited_options() instead.)
This patch should incur only two visible changes, both for child_format
children, both of which are effectively bug fixes:
First, they no longer have discard=unmap set by default. This reason it
was set is because bdrv_inherited_fmt_options() fell through to
bdrv_protocol_options(), and that set it because "format drivers take
care to send flushes and respect unmap policy". None of the drivers
that use child_format for their children (quorum and blkverify) are
format drivers, though, so this reasoning does not apply here.
Second, they no longer have BDRV_O_NO_IO force-cleared. child_format
was used solely for children that do not store any metadata and as such
will not be accessed by their parents as long as those parents do not
receive I/O themselves. Thus, such children should inherit
BDRV_O_NO_IO.
Signed-off-by: Max Reitz <mre...@redhat.com>
---
block.c | 71 +++++++++++++++------------------------------------------
1 file changed, 19 insertions(+), 52 deletions(-)
Reviewed-by: Eric Blake <ebl...@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
