similar to: [PATCH nbdkit v2 0/4] tests: Test export flags (eflags).

Some feature additions to the shell script plugin allow us to test the export flags field reasonably easily. Rich.

When I added .can_FOO caching in 1.16, I missed the case that the sh plugin itself was calling .can_flush twice in some situations (in order to default .can_fua). Then right after, I regressed it to call .can_zero twice (in order to default .can_fast_zero). I also missed that .thread_model could use better caching, because at the time, I did not add testsuite coverage. Fix that now. Eric Blake

I'm still working my way through the filters before this series will be complete, but this is enough of a start to at least get some feedback on the idea of implementing another NBD protocol extension. Eric Blake (9): server: Internal hooks for implementing NBD_CMD_CACHE plugins: Add .cache callback file, split: Implement .cache with posix_fadvise nbd: Implement NBD_CMD_CACHE

This is a cover letter to a series of patches being proposed in tandem to four different projects: - nbd: Document a new NBD_CMD_FLAG_FAST_ZERO command flag - qemu: Implement the flag for both clients and server - libnbd: Implement the flag for clients - nbdkit: Implement the flag for servers, including the nbd passthrough client If you want to test the patches together, I've pushed a

Rich pointed out that making thread_model dynamic even for plugins makes some sense, so here is the code for doing it for 'sh'. I'm less confident on how to do it for OCaml and Rust (not to mention that those allow the plugin to already compile in their model, rather than the language binding glue forcing a model). The other languages (lua, perl, python, ruby) still need to be

In commit c306fa93ab and neighbors (v1.15.1), a concerted effort went into caching the results of .can_FOO callbacks, with commit messages demonstrating that a plugin with a slow callback should not have that delay magnified multiple times. But nothing was added to the testsuite at the time, and with the sh and eval plugins, we still have two scenarios where we did not take advantage of the

Since v1: - rework .can_cache to be tri-state, with default of no advertisement (ripple effect through other patches) - add a lot more patches in order to round out filter support And in the meantime, Rich pushed NBD_CMD_CACHE support into libnbd, so in theory we now have a way to test cache commands through the entire stack. Eric Blake (24): server: Internal hooks for implementing

This allows us to add the following callbacks: - can_zero returns boolean - can_fua should print "none", "emulate" or "native" Furthermore the following callbacks are modified in a backwards compatible manner: - pwrite adding flags parameter - trim adding flags parameter This change is not backwards compatible: - zero may_trim

--- tests/Makefile.am | 3 + tests/test-eflags.sh | 222 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 225 insertions(+) diff --git a/tests/Makefile.am b/tests/Makefile.am index a01c47c..173d622 100644 --- a/tests/Makefile.am +++ b/tests/Makefile.am @@ -282,6 +282,9 @@ test_oldstyle_LDADD = libtest.la $(LIBGUESTFS_LIBS) endif HAVE_LIBGUESTFS +# Test export flags. +TESTS

Allow plugins to affect the handling of the new NBD_CMD_FLAG_FAST_ZERO flag, then update affected plugins. In particular, in-memory plugins are always fast; the full plugin is better served by omitting .zero and relying on .pwrite fallback; nbd takes advantage of libnbd extensions proposed in parallel to pass through support; and v2 language bindings expose the choice to their scripts. The

This allows us to add the following callbacks: - can_zero returns boolean - can_fua should print "none", "emulate" or "native" Furthermore the following callbacks are modified in a backwards compatible manner: - pwrite adding flags parameter - trim adding flags parameter This change is not backwards compatible: - zero may_trim

It's easy to expose new callbacks to sh plugins, by borrowing tri-state code from can_fua. It's possible that nbdkit emulate will actually work well (in our example.sh script, the kernel caching a pread from one dd invocation may indeed speed up the next access), but for the sake of the example, I demonstrated advertising a no-op handler. The shell plugin, coupled with Rich's work on

Until the next few patches expose and implement new callbacks for filters and plugins, our initial implementation for NBD_CMD_CACHE is to just blindly advertise the feature, and call into .pread with an ignored buffer. Note that for bisection reasons, this patch treats any use of a filter as a forced .can_cache of false to bypass the filter's caching; once all affected filters are patched to

This is a revision of my .default_export work, plus new work on .export_descriptions and a new exportname filter. I think it is now ready to check in. Things I'd still like in 1.22: - the file plugin should implement .list_exports (patch already posted, but it needs rebasing on this series) - the ext2 filter should override .list_exports when in exportname mode - the nbd plugin should be

If you're following nbdkit development upstream you'll have seen that we are still making changes to the .list_exports and related APIs. The current .list_exports API upstream is not how it will look finally. The latest set of proposals was here: https://www.redhat.com/archives/libguestfs/2020-August/thread.html#00330 At the same time I'd like to do an nbdkit 1.22 (stable) release.

Since v1: - patch 1: check size limits - patch 2: better handling of default export name canonicalization - patch 3: support filters as well as plugins - patch 4: new - patch 5: rewrite sh parser, fix testsuite to actually work and cover more cases (now that libnbd.git is fixed) Eric Blake (4): server: Add exports list functions server: Prepare to use export list from plugin log: Add

It's been several weeks since I posted v2 (I got distracted by improving libnbd to better test things, which in turn surfaced some major memory leak problems in nbdsh that are now fixed). Many of the patches are minor rebases from v2, with the biggest changes being fallout from: - patch 2: rename nbdkit_add_default_export to nbdkit_use_default_export - overall: this missed 1.22, so update

This is a subset of the last half of the larger 9-patch series. The uncontroversial first half of that series is pushed, but here, I tried to reduce the size of the patches by splitting out some of the more complex changes, so that the rest of the changes remaining in the series are more mechanical. In turn, it forced me to write timing tests, which let me spot another spot where we are wasting

v1: https://www.redhat.com/archives/libguestfs/2019-November/msg00153.html v2: - Fix implementation of can_cache. - Add implementation of can_fua. - Add a very thorough test suite which tests every command + flag combination.

When we added support for .extents, we had nbdkit unconditionally support structured replies if the client requests them, and the plugin's .can_extents has no impact on what the server advertises. However, while the plugin API doesn't care whether the client requested SR, there is still a case to be made for allowing a filter to prevent SR, at least for testing purposese (such as