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Re: [PATCH v2 0/4] nbd/server: Quiesce coroutines on context switch
From: |
Sergio Lopez |
Subject: |
Re: [PATCH v2 0/4] nbd/server: Quiesce coroutines on context switch |
Date: |
Thu, 21 Jan 2021 06:57:15 +0100 |
On Wed, Jan 20, 2021 at 02:49:14PM -0600, Eric Blake wrote:
> On 12/14/20 11:05 AM, Sergio Lopez wrote:
> > This series allows the NBD server to properly switch between AIO contexts,
> > having quiesced recv_coroutine and send_coroutine before doing the
> > transition.
> >
> > We need this because we send back devices running in IO Thread owned
> > contexts
> > to the main context when stopping the data plane, something that can happen
> > multiple times during the lifetime of a VM (usually during the boot
> > sequence or
> > on a reboot), and we drag the NBD server of the correspoing export with it.
> >
> > While there, fix also a problem caused by a cross-dependency between
> > closing the export's client connections and draining the block
> > layer. The visible effect of this problem was QEMU getting hung when
> > the guest request a power off while there's an active NBD client.
> >
> > v2:
> > - Replace "virtio-blk: Acquire context while switching them on
> > dataplane start" with "block: Honor blk_set_aio_context() context
> > requirements" (Kevin Wolf)
> > - Add "block: Avoid processing BDS twice in
> > bdrv_set_aio_context_ignore()"
> > - Add "block: Close block exports in two steps"
> > - Rename nbd_read_eof() to nbd_server_read_eof() (Eric Blake)
> > - Fix double space and typo in comment. (Eric Blake)
>
> ping - where do we stand on this series? Patches 1 and 3 have positive
> reviews, I'll queue them now; patches 2 and 4 had enough comments that
> I'm guessing I should wait for a v3?
Yes, I have almost ready a v3. Will send it out today. I think it'd be
better to pull all four patches at the same time, as "block: Honor
blk_set_aio_context() context requirements" may cause trouble without
the patch to avoid double processing in
"bdrv_set_aio_context_ignore()".
Thanks,
Sergio.
> >
> > Sergio Lopez (4):
> > block: Honor blk_set_aio_context() context requirements
> > block: Avoid processing BDS twice in bdrv_set_aio_context_ignore()
> > nbd/server: Quiesce coroutines on context switch
> > block: Close block exports in two steps
> >
> > block.c | 27 ++++++-
> > block/export/export.c | 10 +--
> > blockdev-nbd.c | 2 +-
> > hw/block/dataplane/virtio-blk.c | 4 ++
> > hw/block/dataplane/xen-block.c | 7 +-
> > hw/scsi/virtio-scsi.c | 6 +-
> > include/block/export.h | 4 +-
> > nbd/server.c | 120 ++++++++++++++++++++++++++++----
> > qemu-nbd.c | 2 +-
> > stubs/blk-exp-close-all.c | 2 +-
> > 10 files changed, 156 insertions(+), 28 deletions(-)
> >
>
> --
> Eric Blake, Principal Software Engineer
> Red Hat, Inc. +1-919-301-3226
> Virtualization: qemu.org | libvirt.org
>
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