search for: nbdkit_fua_none

Two hopefully useful additions to the fua filter. The second one is kind of like cache=unsafe in qemu, in that it exchanges correctness for speed. Useful for data which is easily recreated in the event of a crash or for people who like living on the edge and have good backups. Rich.

On Wed, Apr 11, 2018 at 12:03:41AM -0500, Eric Blake wrote: > +=item C<can_fua> > + > +(Optional) > + > + def can_fua(h): > + # return a boolean > + > +Unlike the C counterpart, the Python callback does not need a > +tri-state return value, because Python introspection is sufficient to > +learn whether callbacks support FUA. Thus, this function only returns

...tant (m, "FLAG_FUA", NBDKIT_FLAG_FUA); > + PyModule_AddIntConstant (m, "FLAG_REQ_ONE", NBDKIT_FLAG_REQ_ONE); > + PyModule_AddIntConstant (m, "FLAG_FAST_ZERO", NBDKIT_FLAG_FAST_ZERO); > + > + PyModule_AddIntConstant (m, "FUA_NONE", NBDKIT_FUA_NONE); > + PyModule_AddIntConstant (m, "FUA_EMULATE", NBDKIT_FUA_EMULATE); > + PyModule_AddIntConstant (m, "FUA_NATIVE", NBDKIT_FUA_NATIVE); > + > + PyModule_AddIntConstant (m, "CACHE_NONE", NBDKIT_CACHE_NONE); > + PyModule_AddIntConstant (m, &...

...= { script, "can_fua", h, NULL }; + char *s = NULL; + size_t slen; + int r; + + switch (call_read (&s, &slen, args)) { + case OK: + if (slen > 0 && s[slen-1] == '\n') + s[slen-1] = '\0'; + if (strcmp (s, "none") == 0) + r = NBDKIT_FUA_NONE; + else if (strcmp (s, "emulate") == 0) + r = NBDKIT_FUA_EMULATE; + else if (strcmp (s, "native") == 0) + r = NBDKIT_FUA_NATIVE; + else { + nbdkit_error ("%s: could not parse output from can_fua method: %s", + script, s); +...

...how the Forced Unit Access flag will be handled; it is -only relevant for connections that are not read-only. For now, this -function has no counterpart in plugins, although it will be added. -Unlike other feature functions with just two success states, this one -returns three success values: C<NBDKIT_FUA_NONE> to avoid advertising -FUA support to the client, C<NBDKIT_FUA_EMULATE> if FUA is emulated by -nbdkit calling flush after a write transaction, and +only relevant for connections that are not read-only. This intercepts +the corresponding plugin method, to control feature bits advertised to...

On 3/18/20 8:21 PM, Eric Blake wrote: > 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

...= { script, "can_fua", h, NULL }; + char *s = NULL; + size_t slen; + int r; + + switch (call_read (&s, &slen, args)) { + case OK: + if (slen > 0 && s[slen-1] == '\n') + s[slen-1] = '\0'; + if (strcmp (s, "none") == 0) + r = NBDKIT_FUA_NONE; + else if (strcmp (s, "emulate") == 0) + r = NBDKIT_FUA_EMULATE; + else if (strcmp (s, "native") == 0) + r = NBDKIT_FUA_NATIVE; + else { + nbdkit_error ("%s: could not parse output from can_fua method: %s", + script, s); +...

...KIT_FLAG_FUA); > > > + PyModule_AddIntConstant (m, "FLAG_REQ_ONE", NBDKIT_FLAG_REQ_ONE); > > > + PyModule_AddIntConstant (m, "FLAG_FAST_ZERO", NBDKIT_FLAG_FAST_ZERO); > > > + > > > + PyModule_AddIntConstant (m, "FUA_NONE", NBDKIT_FUA_NONE); > > > + PyModule_AddIntConstant (m, "FUA_EMULATE", NBDKIT_FUA_EMULATE); > > > + PyModule_AddIntConstant (m, "FUA_NATIVE", NBDKIT_FUA_NATIVE); > > > + > > > + PyModule_AddIntConstant (m, "CACHE_NONE", NBDKIT_CACHE_NONE...

...nt. diff --git a/docs/nbdkit-plugin.pod b/docs/nbdkit-plugin.pod index cfa14b0..c72ea0d 100644 --- a/docs/nbdkit-plugin.pod +++ b/docs/nbdkit-plugin.pod @@ -586,6 +586,26 @@ handle FUA requests. If omitted, nbdkit checks whether C<.flush> exists, and behaves as if this function returns C<NBDKIT_FUA_NONE> or C<NBDKIT_FUA_EMULATE> as appropriate. +=head2 C<.can_multi_conn> + + int can_multi_conn (void *handle); + +This is called during the option negotiation phase to find out if the +plugin can handle multiple connections from a single client. + +Specifically it means that either t...

I'm still working on another set of patches to have reopen call .finalize/.prepare (so that another filter can safely appear between retry and the plugin), but for tonight, these are the patches I think are ready to go. Eric Blake (4): retry: Handle can_fua and can_fast_zero changes tests: Test retry with different fua/fast-zero flags server: Close backends if a filter's .open fails

...PyModule_AddIntConstant (m, "FLAG_FUA", NBDKIT_FLAG_FUA); + PyModule_AddIntConstant (m, "FLAG_REQ_ONE", NBDKIT_FLAG_REQ_ONE); + PyModule_AddIntConstant (m, "FLAG_FAST_ZERO", NBDKIT_FLAG_FAST_ZERO); + + PyModule_AddIntConstant (m, "FUA_NONE", NBDKIT_FUA_NONE); + PyModule_AddIntConstant (m, "FUA_EMULATE", NBDKIT_FUA_EMULATE); + PyModule_AddIntConstant (m, "FUA_NATIVE", NBDKIT_FUA_NATIVE); + + PyModule_AddIntConstant (m, "CACHE_NONE", NBDKIT_CACHE_NONE); + PyModule_AddIntConstant (m, "CACHE_EMULATE",...

...FUA", NBDKIT_FLAG_FUA); > > + PyModule_AddIntConstant (m, "FLAG_REQ_ONE", NBDKIT_FLAG_REQ_ONE); > > + PyModule_AddIntConstant (m, "FLAG_FAST_ZERO", NBDKIT_FLAG_FAST_ZERO); > > + > > + PyModule_AddIntConstant (m, "FUA_NONE", NBDKIT_FUA_NONE); > > + PyModule_AddIntConstant (m, "FUA_EMULATE", NBDKIT_FUA_EMULATE); > > + PyModule_AddIntConstant (m, "FUA_NATIVE", NBDKIT_FUA_NATIVE); > > + > > + PyModule_AddIntConstant (m, "CACHE_NONE", NBDKIT_CACHE_NONE); > > + PyMo...

...into the nbdkit tristate. */ + if (callback_defined ("can_fua", &fn)) { + PyErr_Clear (); + + r = PyObject_CallFunctionObjArgs (fn, obj, NULL); + Py_DECREF (fn); + if (check_python_failure ("can_fua") == -1) + return -1; + if (r == Py_False) + fua = NBDKIT_FUA_NONE; + else if (pwrite_has_fua || zero_has_fua || trim_has_fua) + fua = NBDKIT_FUA_NATIVE; + else + fua = NBDKIT_FUA_EMULATE; + Py_DECREF (r); + } + else if (pwrite_has_fua || zero_has_fua || trim_has_fua) + fua = NBDKIT_FUA_NATIVE; + else if (callback_defined ("flush&quot...

v1 was here: https://www.redhat.com/archives/libguestfs/2018-December/thread.html#00123 v2: - Document "-" instead of "script=-" and use it in the test; and verify this also works on FreeBSD; and verify that it doesn't depend on the particular behaviour of our wrapper script and should work with installed nbdkit too. - Fix handling of zero flags parameter. -

...and flush requests for speed > +(although this is unsafe). Also it can be used to test client or > +server fallbacks, and for evaluating timing differences between proper > +use of FUA compared to a full flush. > > =head1 PARAMETERS > > @@ -53,6 +55,15 @@ returns C<NBDKIT_FUA_NONE>. > Pass through FUA and flush requests unchanged. Turns the filter into > a no-op. > > +=item B<fuamode=discard> > + > +The filter will discard FUA and flush requests. > + > +B<This mode is unsafe>: If the NBD disk contains a filesystem then you >...

After more than a month since v2 [1], I've finally got my FUA support series polished. This is all of my outstanding patches, even though some of them were originally posted in separate threads from the original FUA post [2], [3] [1] https://www.redhat.com/archives/libguestfs/2018-January/msg00113.html [2] https://www.redhat.com/archives/libguestfs/2018-January/msg00219.html [3]

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

First thing to say is that I need to do a *lot* more testing on this, so this is just an early peek. In particular, although it passed ‘make check && make check-valgrind’ I have *not* tested it against a multi-conn-aware client such as the Linux kernel >= 4.9. This implements NBD_FLAG_CAN_MULTI_CONN, described in the protocol doc as: "NBD_FLAG_CAN_MULTI_CONN: Indicates that

The immediate reason for this patch is to reduce the amount of debugging in virt-v2v with using the virt-v2v -v option (because this implies running nbdkit in verbose mode too). Most of the messages are datapath ones about pread/pwrite requests, and in fact as we've added more filters on top of nbdkit these messages have got more and more verbose. However they are not particularly

For existing commits, this is almost identical to v1, except that I updated some commit messages and reordered the commits in a somewhat more logical sequence. The main changes are the extra commits: [06/11] plugins: Return NBD_FLAG_CAN_MULTI_CONN from some readonly plugins. - Readonly plugins that can set the flag unconditionally. [09/11] partitioning: Return NBD_FLAG_CAN_MULTI_CONN. [10/11]