From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Hanna Reitz <hreitz@redhat.com>
Cc: Emanuele Giuseppe Esposito <eesposit@redhat.com>,
Kevin Wolf <kwolf@redhat.com>,
Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
Eduardo Habkost <ehabkost@redhat.com>,
qemu-block@nongnu.org, Juan Quintela <quintela@redhat.com>,
qemu-devel@nongnu.org, Eric Blake <eblake@redhat.com>,
Richard Henderson <richard.henderson@linaro.org>,
Markus Armbruster <armbru@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>, Fam Zheng <fam@euphon.net>,
John Snow <jsnow@redhat.com>
Subject: Re: [PATCH v4 00/25] block layer: split block APIs in global state and I/O
Date: Mon, 15 Nov 2021 16:11:15 +0000 [thread overview]
Message-ID: <YZKGo1ZwkaE+zNRT@redhat.com> (raw)
In-Reply-To: <93821bd8-2ac0-a19e-7029-900e6a6d9be1@redhat.com>
On Mon, Nov 15, 2021 at 05:03:28PM +0100, Hanna Reitz wrote:
> On 25.10.21 12:17, Emanuele Giuseppe Esposito wrote:
> > Currently, block layer APIs like block-backend.h contain a mix of
> > functions that are either running in the main loop and under the
> > BQL, or are thread-safe functions and run in iothreads performing I/O.
> > The functions running under BQL also take care of modifying the
> > block graph, by using drain and/or aio_context_acquire/release.
> > This makes it very confusing to understand where each function
> > runs, and what assumptions it provided with regards to thread
> > safety.
> >
> > We call the functions running under BQL "global state (GS) API", and
> > distinguish them from the thread-safe "I/O API".
> >
> > The aim of this series is to split the relevant block headers in
> > global state and I/O sub-headers.
>
> Despite leaving quite some comments, the series and the split seem
> reasonable to me overall. (This is a pretty big series, after all, so those
> “some comments” stack up against a majority of changes that seem OK to me.
> :))
>
> One thing I noticed while reviewing is that it’s really hard to verify that
> no I/O function calls a GS function. What would be wonderful is some
> function marker like coroutine_fn that marks GS functions (or I/O functions)
> and that we could then verify the call paths. But AFAIU we’ve always wanted
> precisely that for coroutine_fn and still don’t have it, so this seems like
> extremely wishful thinking... :(
Even if we don't programmatically verify these rules, it would be a major
step forward if we simply adopted a standard naming convention for the
APIs that was essentally self-describing. eg block_io_XXX for all I/O
stuff and block_state_XXXX for all global state ,and block_common if
we have stuff applicable to both use cases.
I wouldn't suggest doing it as part of this series, but I think it'd
be worthwhile in general for the medium-long term, despite the code
churn in updating all usage in the short term.
Regards,
Daniel
--
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next prev parent reply other threads:[~2021-11-15 16:13 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-25 10:17 [PATCH v4 00/25] block layer: split block APIs in global state and I/O Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 01/25] main-loop.h: introduce qemu_in_main_thread() Emanuele Giuseppe Esposito
2021-10-25 11:33 ` Philippe Mathieu-Daudé
2021-10-25 10:17 ` [PATCH v4 02/25] include/block/block: split header into I/O and global state API Emanuele Giuseppe Esposito
2021-10-25 11:37 ` Philippe Mathieu-Daudé
2021-10-25 12:22 ` Emanuele Giuseppe Esposito
2021-11-11 15:00 ` Hanna Reitz
2021-11-15 12:08 ` Emanuele Giuseppe Esposito
2021-11-12 12:25 ` Hanna Reitz
2021-11-16 14:00 ` Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 03/25] assertions for block " Emanuele Giuseppe Esposito
2021-11-11 16:32 ` Hanna Reitz
2021-11-15 12:27 ` Emanuele Giuseppe Esposito
2021-11-15 15:27 ` Hanna Reitz
2021-11-12 11:31 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 04/25] include/sysemu/block-backend: split header into I/O and global state (GS) API Emanuele Giuseppe Esposito
2021-11-12 10:23 ` Hanna Reitz
2021-11-16 10:16 ` Emanuele Giuseppe Esposito
2021-11-12 12:30 ` Hanna Reitz
2021-11-16 14:24 ` Emanuele Giuseppe Esposito
2021-11-16 15:07 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 05/25] block/block-backend.c: assertions for block-backend Emanuele Giuseppe Esposito
2021-11-12 11:01 ` Hanna Reitz
2021-11-16 10:15 ` Emanuele Giuseppe Esposito
2021-11-16 12:29 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 06/25] include/block/block_int: split header into I/O and global state API Emanuele Giuseppe Esposito
2021-11-12 12:17 ` Hanna Reitz
2021-11-16 10:24 ` Emanuele Giuseppe Esposito
2021-11-16 12:30 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 07/25] assertions for block_int " Emanuele Giuseppe Esposito
2021-11-12 13:51 ` Hanna Reitz
2021-11-16 15:43 ` Emanuele Giuseppe Esposito
2021-11-16 16:46 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 08/25] block: introduce assert_bdrv_graph_writable Emanuele Giuseppe Esposito
2021-11-12 14:40 ` Hanna Reitz
2021-11-18 9:55 ` Emanuele Giuseppe Esposito
2021-11-18 10:24 ` Emanuele Giuseppe Esposito
2021-11-18 15:17 ` Hanna Reitz
2021-11-19 8:55 ` Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 09/25] include/block/blockjob_int.h: split header into I/O and GS API Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 10/25] assertions for blockjob_int.h Emanuele Giuseppe Esposito
2021-11-12 15:17 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 11/25] include/block/blockjob.h: global state API Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 12/25] assertions for blockob.h " Emanuele Giuseppe Esposito
2021-11-12 15:26 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 13/25] include/sysemu/blockdev.h: move drive_add and inline drive_def Emanuele Giuseppe Esposito
2021-11-12 15:41 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 14/25] include/systemu/blockdev.h: global state API Emanuele Giuseppe Esposito
2021-10-28 15:48 ` Stefan Hajnoczi
2021-11-12 15:46 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 15/25] assertions for blockdev.h " Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 16/25] include/block/snapshot: global state API + assertions Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 17/25] block/copy-before-write.h: " Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 18/25] block/coroutines: I/O API Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 19/25] block_int-common.h: split function pointers in BlockDriver Emanuele Giuseppe Esposito
2021-11-15 12:00 ` Hanna Reitz
2021-11-18 12:42 ` Emanuele Giuseppe Esposito
2021-10-25 10:17 ` [PATCH v4 20/25] block_int-common.h: assertion in the callers of BlockDriver function pointers Emanuele Giuseppe Esposito
2021-11-15 12:48 ` Hanna Reitz
2021-11-15 14:15 ` Hanna Reitz
2021-11-17 11:33 ` Emanuele Giuseppe Esposito
2021-11-17 12:51 ` Hanna Reitz
2021-11-17 13:09 ` Emanuele Giuseppe Esposito
2021-11-17 13:34 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 21/25] block_int-common.h: split function pointers in BdrvChildClass Emanuele Giuseppe Esposito
2021-11-15 14:36 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 22/25] block_int-common.h: assertions in the callers of BdrvChildClass function pointers Emanuele Giuseppe Esposito
2021-11-15 14:48 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 23/25] block-backend-common.h: split function pointers in BlockDevOps Emanuele Giuseppe Esposito
2021-10-25 14:10 ` Philippe Mathieu-Daudé
2021-10-25 10:17 ` [PATCH v4 24/25] job.h: split function pointers in JobDriver Emanuele Giuseppe Esposito
2021-11-15 15:11 ` Hanna Reitz
2021-11-17 13:43 ` Emanuele Giuseppe Esposito
2021-11-17 13:44 ` Hanna Reitz
2021-10-25 10:17 ` [PATCH v4 25/25] job.h: assertions in the callers of JobDriver funcion pointers Emanuele Giuseppe Esposito
2021-10-25 14:09 ` [PATCH v4 00/25] block layer: split block APIs in global state and I/O Philippe Mathieu-Daudé
2021-10-28 15:45 ` Stefan Hajnoczi
2021-10-28 15:49 ` Stefan Hajnoczi
2021-11-15 16:03 ` Hanna Reitz
2021-11-15 16:11 ` Daniel P. Berrangé [this message]
2021-11-18 13:50 ` Paolo Bonzini
2021-11-18 15:31 ` Hanna Reitz
2021-11-19 3:13 ` Paolo Bonzini
2021-11-19 10:42 ` Emanuele Giuseppe Esposito
2021-11-18 14:04 ` Paolo Bonzini
2021-11-18 15:22 ` Hanna Reitz
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