Re: [PATCH v2 00/19] block: Some multi-threading fixes

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Nov 10, 2025 at 04:48:35PM +0100, Hanna Czenczek wrote:
> Hi,
> 
> See the v1 cover letter for a general overview:
> 
> https://lists.nongnu.org/archive/html/qemu-block/2025-10/msg00501.html
> 
> Changes in v2:
> - Kept `.ret = EINPGORESS`-style initializations where they already had
>   been (curl, nvme)
> - Dropped trivial BH waking code (i.e. which can be directly replaced by
>   aio_co_wake()) in iscsi, nfs, nvme
> - curl: Yield in curl_do_preadv() (former curl_setup_preadv()) and
>   curl_find_buf() instead of returning whether curl_co_preadv() has to
>   yield or not
> - nvme: Added a patch that annotates some functions (primarily BHs and
>   CBs) with which AioContext they (must) run in
> - qcow2 cache-cleaning timer: Run the timer as a coroutine instead of in
>   a timer CB; use a CoQueue to await it exiting instead of polling
>   (well, we still need to poll in case we don’t run in a coroutine, but
>   that’s standard procedure, I believe)
>   - The need to initialize the CoQueue showed that there is a code path
>     in qcow2 that doesn’t initialize its CoMutex.  Added a patch to do
>     that.
>   - Also added a patch to have the timer use realtime instead of virtual
>     time.
> 
> 
> git backport-diff against v1:
> 
> Key:
> [----] : patches are identical
> [####] : number of functional differences between upstream/downstream patch
> [down] : patch is downstream-only
> The flags [FC] indicate (F)unctional and (C)ontextual differences, respectively
> 
> 001/19:[----] [--] 'block: Note on aio_co_wake use if not yet yielding'
> 002/19:[----] [--] 'rbd: Run co BH CB in the coroutine’s AioContext'
> 003/19:[0019] [FC] 'iscsi: Run co BH CB in the coroutine’s AioContext'
> 004/19:[0022] [FC] 'nfs: Run co BH CB in the coroutine’s AioContext'
> 005/19:[0060] [FC] 'curl: Fix coroutine waking'
> 006/19:[----] [--] 'gluster: Do not move coroutine into BDS context'
> 007/19:[----] [--] 'nvme: Kick and check completions in BDS context'
> 008/19:[0038] [FC] 'nvme: Fix coroutine waking'
> 009/19:[down] 'nvme: Note in which AioContext some functions run'
> 010/19:[----] [--] 'block/io: Take reqs_lock for tracked_requests'
> 011/19:[down] 'qcow2: Re-initialize lock in invalidate_cache'
> 012/19:[0145] [FC] 'qcow2: Fix cache_clean_timer'
> 013/19:[down] 'qcow2: Schedule cache-clean-timer in realtime'
> 014/19:[----] [--] 'ssh: Run restart_coroutine in current AioContext'
> 015/19:[----] [--] 'blkreplay: Run BH in coroutine’s AioContext'
> 016/19:[----] [--] 'block: Note in which AioContext AIO CBs are called'
> 017/19:[----] [--] 'iscsi: Create AIO BH in original AioContext'
> 018/19:[----] [--] 'null-aio: Run CB in original AioContext'
> 019/19:[----] [--] 'win32-aio: Run CB in original context'
> 
> 
> Hanna Czenczek (19):
>   block: Note on aio_co_wake use if not yet yielding
>   rbd: Run co BH CB in the coroutine’s AioContext
>   iscsi: Run co BH CB in the coroutine’s AioContext
>   nfs: Run co BH CB in the coroutine’s AioContext
>   curl: Fix coroutine waking
>   gluster: Do not move coroutine into BDS context
>   nvme: Kick and check completions in BDS context
>   nvme: Fix coroutine waking
>   nvme: Note in which AioContext some functions run
>   block/io: Take reqs_lock for tracked_requests
>   qcow2: Re-initialize lock in invalidate_cache
>   qcow2: Fix cache_clean_timer
>   qcow2: Schedule cache-clean-timer in realtime
>   ssh: Run restart_coroutine in current AioContext
>   blkreplay: Run BH in coroutine’s AioContext
>   block: Note in which AioContext AIO CBs are called
>   iscsi: Create AIO BH in original AioContext
>   null-aio: Run CB in original AioContext
>   win32-aio: Run CB in original context
> 
>  block/qcow2.h                    |   5 +-
>  include/block/aio.h              |  15 ++++
>  include/block/block_int-common.h |   7 +-
>  block/blkreplay.c                |   3 +-
>  block/curl.c                     |  45 +++++++---
>  block/gluster.c                  |  17 ++--
>  block/io.c                       |   3 +
>  block/iscsi.c                    |  63 ++++++--------
>  block/nfs.c                      |  41 ++++-----
>  block/null.c                     |   7 +-
>  block/nvme.c                     | 113 ++++++++++++++++--------
>  block/qcow2.c                    | 145 ++++++++++++++++++++++++-------
>  block/rbd.c                      |  12 +--
>  block/ssh.c                      |  22 ++---
>  block/win32-aio.c                |  31 +++++--
>  15 files changed, 347 insertions(+), 182 deletions(-)
> 
> -- 
> 2.51.1
> 

I reviewed the nvme changes and the core block layer changes:

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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