The way that attaching bs->file worked was a bit unusual in that it was
the only child that would be attached to a node which is not opened yet.
Because of this, the block layer couldn't know yet which permissions the
driver would eventually need.
This patch moves the point where bs->file is attached to the beginning
of the individual .bdrv_open() implementations, so drivers already know
what they are going to do with the child. This is also more consistent
with how driver-specific children work.
For a moment, bdrv_open() gets its own BdrvChild to perform image
probing, but instead of directly assigning this BdrvChild to the BDS, it
becomes a temporary one and the node name is passed as an option to the
drivers, so that they can simply use bdrv_open_child() to create another
reference for their own use.
This duplicated child for (the not opened yet) bs is not the final
state, a follow-up patch will change the image probing code to use a
BlockBackend, which is completely independent of bs.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
=== This is the QEMU I/O test suite ===
* Intro
This package contains a simple test suite for the I/O layer of qemu.
It does not require a guest, but only the qemu, qemu-img and qemu-io
binaries. This does limit it to exercise the low-level I/O path only
but no actual block drivers like ide, scsi or virtio.
* Usage
Just run ./check to run all tests for the raw image format, or ./check
-qcow2 to test the qcow2 image format. The output of ./check -h explains
additional options to test further image formats or I/O methods.
* Feedback and patches
Please send improvements to the test suite, general feedback or just
reports of failing tests cases to qemu-devel@nongnu.org with a CC:
to qemu-block@nongnu.org.
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