On 03/29/2017 10:01 PM, Ed Swierk via Qemu-devel wrote: > Parts of qemu's block code have changed a lot in recent months but are > not well exercised by current tests. > > Subtle bugs have crept in causing assertion failures, hangs and other > crashes in a variety of situations: immediately on start, on first > guest activity, on external snapshot create or commit, on qmp quit > command. > > Reproducing these bugs has proved tricky, as each may occur only with > a specific combination of qemu version, block device type (virtio-blk > or virtio-scsi) and iothread enabled or not. In some cases the bug > occurs only after several external snapshot operations. And in some > cases the bug only manifests when a guest is accessing the block > device simultaneously. > > I've written an iotest (number 176, for now) that attempts to cover > many of these configurations. Currently it only exercises the external > snapshot create and commit lifted from iotest 118. The new iotest does > this repeatedly in each of 16 combinations: > - no guest / guest > - virtio-blk / virtio-scsi > - no iothread / iothread > - single / repeated external snapshot create+commit > > I made some minor changes to the test infrastructure so the new iotest > can deal gracefully with qemu hanging--the test script itself > shouldn't hang. And in all failure modes the test needs to expose > enough console output and other information to diagnose the problem. > > The main departure from existing iotests is running a real guest. I > used buildroot to generate a small (~4 MB) Linux kernel with built-in > initrd containing a busybox-based userland. After the iotest launches > qemu, the guest loops writing to the block device, while the test > performs snapshot operations. > > I ran the new iotest on 3 qemu versions: 2.7.1, stable-2.8-staging and > 2.9.0-rc2. The latter two fail several test cases, all > iothread-enabled. Only 2.7.1 passes all the cases. > > Here is the code for the new iotest (I didn't dare email patches with > a 4 MB blob): > https://github.com/skyportsystems/qemu-1/commits/eswierk-iotests-2.7 > https://github.com/skyportsystems/qemu-1/commits/eswierk-iotests-2.8 > https://github.com/skyportsystems/qemu-1/commits/eswierk-iotests-2.9 > > And here is the buildroot I used to generate the guest Linux kernel+initrd: > https://github.com/skyportsystems/buildroot-1/commits/qemu-iotests > > Please check out the code and try the new test--particularly anyone > who can also help figure out these failures. (Note that since half the > test cases use an iothread, /dev/kvm must be readable and writable.) > > * stable-2.8-staging > - guest, virtio-blk, iothread, single snapshot create+commit: hang on > quit (intermittent) > - guest, virtio-blk, iothread, repeated snapshot create+commit: hang > after 1 iteration > - guest, virtio-scsi, iothread, single snapshot create+commit: hang on > quit (intermittent) > - guest, virtio-scsi, iothread, repeated snapshot create+commit: hang > after 1 iteration > > * 2.9.0-rc2 > - guest, virtio-blk, iothread, single snapshot create+commit: > "include/block/aio.h:457: aio_enable_external: Assertion > `ctx->external_disable_cnt > 0' failed." after snapshot create > - guest, virtio-blk, iothread, repeated snapshot create+commit: same as above > - guest, virtio-scsi, iothread, single snapshot create+commit: same as above > - guest, virtio-scsi, iothread, repeated snapshot create+commit: same as above > - no guest, virtio-blk, iothread, repeated snapshot create+commit: same as > above > - no guest, virtio-scsi, iothread, single snapshot create+commit: same as > above > - no guest, virtio-scsi, iothread, repeated snapshot create+commit: > same as above >
Do you mean to say that all of these 2.9.0-rc2 cases produce the same aio.h assertion? > --Ed >
