[Libguestfs] [PATCH nbdkit 6/8] python: Implement cache, can_cache.

--- plugins/python/nbdkit-python-plugin.pod | 22 +++++++++++-- plugins/python/python.c | 41 +++++++++++++++++++++++++ 2 files changed, 61 insertions(+), 2 deletions(-) diff --git a/plugins/python/nbdkit-python-plugin.pod b/plugins/python/nbdkit-python-plugin.pod index 0fd4dcb..2bc4722 100644 --- a/plugins/python/nbdkit-python-plugin.pod +++ b/plugins/python/nbdkit-python-plugin.pod @@ -212,6 +212,13 @@ contents will be garbage collected. def can_trim(h): # return a boolean +=item C<can_cache> + +(Optional) + + def can_cache(h): + # return a boolean + =item C<pread> (Required) @@ -293,6 +300,19 @@ because there is nothing to optimize if S<C<flags & nbdkit.FLAG_MAY_TRIM>> is false), use S<C<nbdkit.set_error (errno.EOPNOTSUPP)>>. +=item C<cache> + +(Optional) + + def cache(h, count, offset, flags): + # no return value + +The body of your C<cache> function should prefetch data in the +indicated range. + +If the cache operation fails, your function should throw an exception, +optionally using C<nbdkit.set_error> first. + =back =head2 Missing callbacks @@ -316,12 +336,10 @@ C<description>, C<config_help>, C<magic_config_key>, C<can_fua>, -C<can_cache>, C<can_zero>, C<can_fast_zero>, C<can_extents>, C<can_multi_conn>, -C<cache>, C<extents>. These are not yet supported. diff --git a/plugins/python/python.c b/plugins/python/python.c index 9445343..33fb6e4 100644 --- a/plugins/python/python.c +++ b/plugins/python/python.c @@ -683,6 +683,39 @@ py_zero (void *handle, uint32_t count, uint64_t offset, uint32_t flags) return -1; } +static int +py_cache (void *handle, uint32_t count, uint64_t offset, uint32_t flags) +{ + PyObject *obj = handle; + PyObject *fn; + PyObject *r; + + if (callback_defined ("cache", &fn)) { + PyErr_Clear (); + + switch (py_api_version) { + case 1: + nbdkit_error ("%s can only be called when using api_version >= 2", + "cache"); + return -1; + case 2: + r = PyObject_CallFunction (fn, "OiLI", obj, count, offset, flags, NULL); + break; + default: abort (); + } + Py_DECREF (fn); + if (check_python_failure ("cache") == -1) + return -1; + Py_DECREF (r); + } + else { + nbdkit_error ("%s not implemented", "cache"); + return -1; + } + + return 0; +} + static int boolean_callback (void *handle, const char *can_fn, const char *plain_fn) { @@ -736,6 +769,12 @@ py_can_trim (void *handle) return boolean_callback (handle, "can_trim", "trim"); } +static int +py_can_cache (void *handle) +{ + return boolean_callback (handle, "can_cache", "cache"); +} + #define py_config_help \ "script=<FILENAME> (required) The Python plugin to run.\n" \ "[other arguments may be used by the plugin that you load]" @@ -762,12 +801,14 @@ static struct nbdkit_plugin plugin = { .can_write = py_can_write, .can_flush = py_can_flush, .can_trim = py_can_trim, + .can_cache = py_can_cache, .pread = py_pread, .pwrite = py_pwrite, .flush = py_flush, .trim = py_trim, .zero = py_zero, + .cache = py_cache, }; NBDKIT_REGISTER_PLUGIN (plugin) -- 2.23.0