similar to: [libnbd PATCH 0/2] Better handling of failed block_status callback

On 6/4/19 4:59 AM, Richard W.M. Jones wrote: > Callback functions now return an int instead of a void. This allows > in some cases for the callback to indicate that there was an error. > > This is a small change to the API: Indeed; and my work to let nbdkit-nbd use libnbd is slightly impacted. If I want to support both 0.1.2 and 0.1.x, I now have to do a conditional compilation

If the user's extent_fn callback fails, we want to fail the overall block status command with the same errno, but not give up on the server. Do this by skipping any further context chunks from the server, and relying on the previous patch's ability to preserve the first error encountered. Update the interop test with qemu's dirty bitmap context to provoke callback failure, as well as

v1: https://www.redhat.com/archives/libguestfs/2019-June/msg00014.html I pushed a few bits which are uncontroversial. The main changes since v1 are: An extra patch removes the want_to_send / check for nbd_aio_is_ready in examples/threaded-reads-and-writes.c. This logic was wrong since commit 6af72b87 as was pointed out by Eric in his review. Comments and structure of

On Wed, Aug 02, 2023 at 08:50:21PM -0500, Eric Blake wrote: > Previously, we had not been doing any validation of server extent > responses, which means a client query at an offset near the end of the > export can result in a buggy server sending a response longer than the > export length and potentially confusing the client. The NBD spec also > says that an extent length should be

Now that we have a way to pass Mutable(Int "error") to callbacks, that's a much nicer way for language bindings to use than relying on the value of errno after returning -1. Update the semantics for block status to match what pread_structured does, getting errno out of the equation, and changing things to call the callback for a second context even after an earlier callback failure

This isn't quite finished because not all of the tests or examples have been updated, but it demonstrates an idea: Should we forget about the concept of having multiple connections managed under a single handle? In this patch there is a single ‘struct nbd_handle *’ which manages a single state machine and connection (and therefore no nbd_connection). To connect to a multi-conn server you must

I've mentioned this topic before (in fact, the idea of adding NBD_CMD_FLAG_DF was first mentioned at [1]), but finally finished enough of an implementation to feel confident in posting it. I'd still like to add something under examples/ that uses the new API to implement strict checking of a server's structured replies read implementation (ensure that a server never sends data after

** INCOMPLETE ** This is the generator change as discussed on the list already. The Python and OCaml bindings are not yet done. It passes all [C only] tests and valgrind. Note that nbd_add_close_callback is inconsistent with other closure types because it passes the user_data parameter after the function. (This is not caused by the current patch, it was already inconsistent). We decided that

This just defines the namespace, its contexts and related constants and the only supported one is currently base:allocation. The names of the constants are not very future-proof, but shorter than LIBNBD_META_NS_CONTEXT_BASE_ALLOCATION or similar. Currently the output looks like this: /* "base" namespace */ /* "base" namespace contexts */ /* "base:allocation"

I think I've addressed everything that was raised in review. Some of the highlights: - Callbacks should be freed reliably along all exit paths. - There's a simple test of closure lifetimes. - I've tried to use VALID|FREE in all the places where I'm confident that it's safe and correct to do. There may be more places. Note this is an optimization and shouldn't

As before, but this one has working Python bindings. OCaml still TBD. Rich.

Patches 1 & 2 are rather complex, but the end result is that we pass closures + user_data + free function in single struct parameters as I described previously in this email: https://www.redhat.com/archives/libguestfs/2019-August/msg00210.html Patch 3 adds a convenient FREE_CALLBACK macro which seems a worthwhile simplification if you buy into 1 & 2. Patch 4 adds another macro which is

v1 was here: https://www.redhat.com/archives/libguestfs/2019-July/thread.html#00231 The changes address everything that Eric picked up in his review of the first two patches. I have also added two more patches (4 and 5) which respectively fix docs and change int status -> unsigned status, as discussed. Passes make, check, check-valgrind. Rich.

This implements most of what I wrote here: https://www.redhat.com/archives/libguestfs/2019-July/msg00213.html

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

I'm posting this now, as I'm at the end of a workday and I got things working for manual experimentation. Still to do: - write interop tests for qemu-nbd and nbdkit (including my proposed patch addition of qemu-nbd -A to show qemu:allocation-depth) - figure out if we can make 'nbdinfo --map' use the new API to automatically select all contexts advertised by the server Eric Blake

Callback functions now return an int instead of a void. This allows in some cases for the callback to indicate that there was an error. This is a small change to the API: For nbd_set_debug_callback the signature has changed, but the return value is ignored. For nbd_block_status and nbd_aio_block_status the extent function can return an error, which causes the block status command to return an

RFC because this is an API break, but we haven't declared stable API yet. If we like it, I'm working on using libnbd to implement the nbdkit-nbd plugin; knowing whether it is API version 0.1 or 0.2 will be useful. I also dabbled with allowing optional parameters in python, although my OCaml is weak enough that there may be cleaner ways to approach that. Eric Blake (4): api: Add flags

The next patch will add a new 'nbd_aio_pread_callback' function for allowing the user more immediate access as each chunk of a structured reply read is received. But before we do that, let's refactor the command code. This includes a revert of 12843a1a, since the read callback will need both a buffer and the user's opaque object at the same time. ---

I'm still playing with ideas on how to split rstate from wstate (so that we can send a request without waiting for POLLIN to complete a pending reply), but this is some preliminary refactoring I found useful. I also fixed a couple of bugs while in the area (already pushed). There's a question of whether we want nbd_handle to be nearly 5k, or if we should instead keep it small and add one