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On 8/13/19 10:37 AM, Richard W.M. Jones wrote: > The original nbd_aio_* (non-callback) functions are removed and > replaced with the renamed callback variants. > > This is a simple mechanical change to the API: > > (1) Any existing call to nbd_aio_*_callback can simply be renamed to > nbd_aio_* > > (2) Any existing call to nbd_aio_* must...

...gt; commands are complete. It's also desirable when writing a server > validation program (such as for checking structured reads for > compliance) to be able to clean up the associated opaque data and have > a final chance to change the overall command status. > > Introduce new nbd_aio_FOO_notify functions for each command. Rewire > the existing nbd_aio_FOO to forward to the new command. (Perhaps the > generator could reduce some of the boilerplate duplication, if a later > patch wants to refactor this). I'm writing some code now using these new nbd_aio_<CMD>_...

This applies on top of the OClosure v2 series posted a few minutes ago. Rich.

The original nbd_aio_* (non-callback) functions are removed and replaced with the renamed callback variants. This is a simple mechanical change to the API: (1) Any existing call to nbd_aio_*_callback can simply be renamed to nbd_aio_* (2) Any existing call to nbd_aio_* must have two extra NULL parameters adde...

...mplete. It's also desirable when writing a server >> validation program (such as for checking structured reads for >> compliance) to be able to clean up the associated opaque data and have >> a final chance to change the overall command status. >> >> Introduce new nbd_aio_FOO_notify functions for each command. Rewire >> the existing nbd_aio_FOO to forward to the new command. (Perhaps the >> generator could reduce some of the boilerplate duplication, if a later >> patch wants to refactor this). > > I'm writing some code now using these ne...

On Fri, Jul 14, 2023 at 09:13:42AM +0200, Laszlo Ersek wrote: > On 7/13/23 21:29, Eric Blake wrote: > > The documentation has claimed since commit 6f4dcdab that any > > completion callback will be called exactly once; but this is not > > consistent with the code: if nbd_aio_* itself returns an error, then > > nothing is queued and the user does not need to wait for a completion > > callback to know how the command failed. We could tweak the generator > > to call completion.callback no matter what, but since the > > completion.free callback alre...

...n Fri, Jul 14, 2023 at 09:13:42AM +0200, Laszlo Ersek wrote: >> On 7/13/23 21:29, Eric Blake wrote: >>> The documentation has claimed since commit 6f4dcdab that any >>> completion callback will be called exactly once; but this is not >>> consistent with the code: if nbd_aio_* itself returns an error, then >>> nothing is queued and the user does not need to wait for a completion >>> callback to know how the command failed. We could tweak the generator >>> to call completion.callback no matter what, but since the >>> completion.free c...

Mutable (Int n) => int *n This can currently only be used for callback arguments of type int (not for other types, nor for any ordinary function arguments), but it could be implemented more generally in future. --- generator/generator | 75 +++++++++++++++++++++++++++++++++++++-------- 1 file changed, 63 insertions(+), 12 deletions(-) diff --git a/generator/generator b/generator/generator

...for the completion signal before reentering the library. (2) If there's some implicit guarantee that we should call the callback as easy as possible after the command finishes. I think (1) is not possible in ordinary code since callers must always enter the main loop after calling one of the nbd_aio_* functions. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. htt...

When using the nbd_aio_FOO_callback commands, there is nothing further to be learned about the command by calling nbd_aio_command_completed() compared to what the callback already had access to. There are still scenarios where manually retiring the command after the fact is useful (whether the return was 0 to keep the st...

We can easily demonstrate a memory leak when repeatedly calling nbd_aio_pread from nbdsh in the wrong state. True, that isn't something a sane client would normally do, but it's worth fixing. The culprit: when nbd_aio_pread returns a cookie, we guarantee to clean up the closure, but if we fail early and never scheduled the command, nothing ever cleans up the c...

...reports errors); we could instead try to go the other direction and tweak the generator to guarantee that both completion.callback and completion.free are reached no matter what, but that felt more invasive to me. Eric Blake (2): api: Tighten rules on completion.callback tests: Add coverage of nbd_aio_opt_* in wrong state docs/libnbd.pod | 26 +++-- lib/handle.c | 3 + lib/opt.c | 2 + tests/Makefile.am | 5 + tests/closure-lifetimes.c | 14 +++ tests/errors-not-negotiating-aio.c | 170 ++++++++++...

...requests. At some point, we may want to add synchronous convenience API wrappers that do request splitting or read-modify-write to obey server constraints while still appearing to the library client as accepting any possible request. But such a wrapper should only be synchronous and not copied to nbd_aio_*, because getting locking right is a bear if you have two non-overlapping client requests that want to visit the same larger-granularity window of the server in parallel. Eric Blake (3): states: Request NBD_INFO_BLOCK_SIZE during NBD_OPT_GO api: Add new API to query negotiated block size nbd...

As promised in my earlier thread on libnbd completion callback question. Eric Blake (2): generator: Refactor handling of closures in unlocked functions generator: Free closures on failure docs/libnbd.pod | 2 +- generator/C.ml | 48 +++++++++++------ generator/C.mli | 1 + lib/debug.c | 7 +-- lib/opt.c | 31 ++++++-----

I still need to wire in the use of *_notify functions into nbdkit to prove whether it makes the code any faster or easier to maintain, but at least the added example shows one good use case for the new API. Eric Blake (6): api: Add nbd_aio_in_flight generator: Allow DEAD state actions to run generator: Allow Int64 in callbacks states: Prepare for aio notify callback api: Add new nbd_aio_FOO_notify functions examples: New example for strict read validations .gitignore | 1 + docs/libnbd....