Although this test is NOT a full test of image fleecing (as it
intentionally uses just a single block device directly exported
over NBD, rather than trying to set up a blockdev-backup job with
multiple BDS involved), it DOES prove that qemu as a server is
able to properly expose a dirty bitmap over NBD.
When coupled with image fleecing, it is then possible for a
third-party client to do an incremental backup by using
qemu-img map with the x-dirty-bitmap option to learn which parts
of the file are dirty (perhaps confusingly, they are the portions
mapped as "data":false - which is part of the reason this is
still in the x- experimental namespace), along with another
normal client (perhaps 'qemu-nbd -c' to expose the server over
/dev/nbd0 and then just use normal I/O on that block device) to
read the dirty sections.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180702191458.28741-3-eblake@redhat.com>
Tested-by: John Snow <jsnow@redhat.com>
Reviewed-by: John Snow <jsnow@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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