An optional Closure parameter, but otherwise works the same way as Closure. --- generator/generator | 57 ++++++++++++++++++++++++++++++++++++--------- 1 file changed, 46 insertions(+), 11 deletions(-) diff --git a/generator/generator b/generator/generator index 8cf95b6..8f15786 100755 --- a/generator/generator +++ b/generator/generator @@ -867,6 +867,7 @@ and arg = | UInt32 of string (* 32 bit unsigned int *) | UInt64 of string (* 64 bit unsigned int *) and optarg = +| OClosure of closure (* optional closure *) | OFlags of string * flags (* optional flags, uint32_t in C *) and ret = | RBool (* return a boolean, or error *) @@ -3184,16 +3185,6 @@ end = struct (* Check the API definition. *) let () = - (* Currently optargs can only be [] or [OFlags]. This condition - * will be relaxed later when we support more optional arguments. - *) - List.iter ( - function - | _, { optargs = [] } | _, { optargs = [OFlags _] } -> () - | (name, _) -> - failwithf "%s: optargs can only be empty list or [OFlags]" name - ) handle_calls; - (* Check functions using may_set_error. *) List.iter ( function @@ -3226,7 +3217,8 @@ let () = | name, { optargs; may_set_error = false } when List.exists (function - | OFlags _ -> true) optargs -> + | OFlags _ -> true + | _ -> false) optargs -> failwithf "%s: if optargs contains an OFlags parameter, may_set_error must be false" name | _ -> () @@ -3388,6 +3380,12 @@ let rec print_arg_list ?(handle = false) ?(types = true) args optargs = if !comma then pr ", "; comma := true; match optarg with + | OClosure { cbname; cbargs } -> + if types then pr "nbd_%s_callback " cbname; + pr "%s_callback" cbname; + pr ", "; + if types then pr "void *"; + pr "%s_user_data" cbname | OFlags (n, _) -> if types then pr "uint32_t "; pr "%s" n @@ -3718,6 +3716,7 @@ let generate_lib_api_c () = ) args; List.iter ( function + | OClosure _ -> () | OFlags (n, flags) -> print_flags_check n flags ) optargs; @@ -3767,6 +3766,7 @@ let generate_lib_api_c () = ) args; List.iter ( function + | OClosure { cbname } -> pr " %s=%%s" cbname | OFlags (n, _) -> pr " %s=0x%%x" n ) optargs; pr "\""; @@ -3789,6 +3789,7 @@ let generate_lib_api_c () = ) args; List.iter ( function + | OClosure { cbname } -> pr ", %s_callback ? \"<fun>\" : \"NULL\"" cbname | OFlags (n, _) -> pr ", %s" n ) optargs; pr ");\n" @@ -4297,6 +4298,8 @@ let print_python_binding name { args; optargs; ret; may_set_error } = ) args; List.iter ( function + | OClosure { cbname } -> + pr " PyObject *%s_user_data;\n" cbname | OFlags (n, _) -> pr " uint32_t %s_u32;\n" n; pr " unsigned int %s; /* really uint32_t */\n" n @@ -4327,6 +4330,7 @@ let print_python_binding name { args; optargs; ret; may_set_error } = ) args; List.iter ( function + | OClosure _ -> pr " \"O\"" | OFlags _ -> pr " \"I\"" ) optargs; pr "\n"; @@ -4353,6 +4357,7 @@ let print_python_binding name { args; optargs; ret; may_set_error } = ) args; List.iter ( function + | OClosure { cbname } -> pr ", &%s_user_data" cbname | OFlags (n, _) -> pr ", &%s" n ) optargs; pr "))\n"; @@ -4394,6 +4399,16 @@ let print_python_binding name { args; optargs; ret; may_set_error } = ) args; List.iter ( function + | OClosure { cbname } -> + pr " if (%s_user_data != Py_None) {\n" cbname; + pr " /* Increment refcount since pointer may be saved by libnbd. */\n"; + pr " Py_INCREF (%s_user_data);\n" cbname; + pr " if (!PyCallable_Check (%s_user_data)) {\n" cbname; + pr " PyErr_SetString (PyExc_TypeError,\n"; + pr " \"callback parameter %s is not callable\");\n" cbname; + pr " return NULL;\n"; + pr " }\n"; + pr " }\n" | OFlags (n, _) -> pr " %s_u32 = %s;\n" n n ) optargs; @@ -4423,6 +4438,9 @@ let print_python_binding name { args; optargs; ret; may_set_error } = ) args; List.iter ( function + | OClosure { cbname } -> + pr ", %s_user_data ? %s_wrapper : NULL" cbname cbname; + pr ", %s_user_data" cbname | OFlags (n, _) -> pr ", %s_u32" n ) optargs; pr ");\n"; @@ -4679,6 +4697,7 @@ class NBD (object): let optargs = List.map ( function + | OClosure { cbname } -> cbname, Some "None", None | OFlags (n, _) -> n, Some "0", None ) optargs in let args = args @ optargs in @@ -4767,6 +4786,8 @@ and ocaml_ret_to_string = function | RUInt -> "int" and ocaml_optarg_to_string = function + | OClosure { cbname; cbargs } -> + sprintf "?%s:(%s)" cbname (ocaml_closuredecl_to_string cbargs) | OFlags (n, { flag_prefix }) -> sprintf "?%s:%s.t list" n flag_prefix and ocaml_closuredecl_to_string cbargs = @@ -4805,6 +4826,7 @@ let ocaml_name_of_arg = function | UInt64 n -> n let ocaml_name_of_optarg = function + | OClosure { cbname } -> cbname | OFlags (n, _) -> n let num_params args optargs = @@ -5213,6 +5235,19 @@ let print_ocaml_binding (name, { args; optargs; ret }) = List.iter ( function + | OClosure { cbname } -> + pr " const void *%s_callback = NULL;\n" cbname; + pr " value *%s_user_data = NULL;\n" cbname; + pr " if (%sv != Val_int (0)) { /* Some closure */\n" cbname; + pr " /* The function may save a reference to the closure, so we\n"; + pr " * must treat it as a possible GC root.\n"; + pr " */\n"; + pr " %s_user_data = malloc (sizeof (value));\n" cbname; + pr " if (%s_user_data == NULL) caml_raise_out_of_memory ();\n" cbname; + pr " *%s_user_data = Field (%sv, 0);\n" cbname cbname; + pr " caml_register_generational_global_root (%s_user_data);\n" cbname; + pr " %s_callback = %s_wrapper;\n" cbname cbname; + pr " }\n"; | OFlags (n, { flag_prefix }) -> pr " uint32_t %s;\n" n; pr " if (%sv != Val_int (0)) /* Some [ list of %s.t ] */\n" -- 2.22.0

On Tue, Aug 13, 2019 at 10:36:23AM -0500, Eric Blake wrote: Right the behaviour on failure of the Python bindings is very difficult. (It should be OK in OCaml because of the way the stack unwinding in OCaml exceptions works). Yes this is buggy - fixed in my copy. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html

This doesn't change the C API, except that it is now permitted to pass NULL, NULL for the completion callback. For the Python and OCaml APIs the parameter changes to be an optional parameter. --- generator/generator | 36 +++++++++---------- ocaml/examples/asynch_copy.ml | 5 +-- .../test_505_aio_pread_structured_callback.ml | 12 ++++--- ocaml/tests/test_590_aio_copy.ml | 5 +-- 4 files changed, 30 insertions(+), 28 deletions(-) diff --git a/generator/generator b/generator/generator index 8f15786..6ccfc5f 100755 --- a/generator/generator +++ b/generator/generator @@ -1836,9 +1836,8 @@ C<nbd_pread>."; "aio_pread_callback", { default_call with - args = [ BytesPersistOut ("buf", "count"); UInt64 "offset"; - Closure completion_closure ]; - optargs = [ OFlags ("flags", cmd_flags) ]; + args = [ BytesPersistOut ("buf", "count"); UInt64 "offset" ]; + optargs = [ OClosure completion_closure; OFlags ("flags", cmd_flags) ]; ret = RInt64; permitted_states = [ Connected ]; shortdesc = "read from the NBD server, with callback on completion"; @@ -1874,9 +1873,8 @@ documented in C<nbd_pread_structured>."; "aio_pread_structured_callback", { default_call with args = [ BytesPersistOut ("buf", "count"); UInt64 "offset"; - Closure chunk_closure; - Closure completion_closure ]; - optargs = [ OFlags ("flags", cmd_flags) ]; + Closure chunk_closure ]; + optargs = [ OClosure completion_closure; OFlags ("flags", cmd_flags) ]; ret = RInt64; permitted_states = [ Connected ]; shortdesc = "read from the NBD server, with callback on completion"; @@ -1910,9 +1908,8 @@ C<nbd_pwrite>."; "aio_pwrite_callback", { default_call with - args = [ BytesPersistIn ("buf", "count"); UInt64 "offset"; - Closure completion_closure ]; - optargs = [ OFlags ("flags", cmd_flags) ]; + args = [ BytesPersistIn ("buf", "count"); UInt64 "offset" ]; + optargs = [ OClosure completion_closure; OFlags ("flags", cmd_flags) ]; ret = RInt64; permitted_states = [ Connected ]; shortdesc = "write to the NBD server, with callback on completion"; @@ -1966,8 +1963,8 @@ Parameters behave as documented in C<nbd_flush>."; "aio_flush_callback", { default_call with - args = [ Closure completion_closure ]; - optargs = [ OFlags ("flags", cmd_flags) ]; + args = []; + optargs = [ OClosure completion_closure; OFlags ("flags", cmd_flags) ]; ret = RInt64; permitted_states = [ Connected ]; shortdesc = "send flush command to the NBD server, with callback on completion"; @@ -1999,8 +1996,8 @@ Parameters behave as documented in C<nbd_trim>."; "aio_trim_callback", { default_call with - args = [ UInt64 "count"; UInt64 "offset"; Closure completion_closure ]; - optargs = [ OFlags ("flags", cmd_flags) ]; + args = [ UInt64 "count"; UInt64 "offset" ]; + optargs = [ OClosure completion_closure; OFlags ("flags", cmd_flags) ]; ret = RInt64; permitted_states = [ Connected ]; shortdesc = "send trim command to the NBD server, with callback on completion"; @@ -2032,8 +2029,8 @@ Parameters behave as documented in C<nbd_cache>."; "aio_cache_callback", { default_call with - args = [ UInt64 "count"; UInt64 "offset"; Closure completion_closure ]; - optargs = [ OFlags ("flags", cmd_flags) ]; + args = [ UInt64 "count"; UInt64 "offset" ]; + optargs = [ OClosure completion_closure; OFlags ("flags", cmd_flags) ]; ret = RInt64; permitted_states = [ Connected ]; shortdesc = "send cache (prefetch) command to the NBD server, with callback on completion"; @@ -2065,8 +2062,8 @@ Parameters behave as documented in C<nbd_zero>."; "aio_zero_callback", { default_call with - args = [ UInt64 "count"; UInt64 "offset"; Closure completion_closure ]; - optargs = [ OFlags ("flags", cmd_flags) ]; + args = [ UInt64 "count"; UInt64 "offset" ]; + optargs = [ OClosure completion_closure; OFlags ("flags", cmd_flags) ]; ret = RInt64; permitted_states = [ Connected ]; shortdesc = "send write zeroes command to the NBD server, with callback on completion"; @@ -2098,9 +2095,8 @@ Parameters behave as documented in C<nbd_block_status>."; "aio_block_status_callback", { default_call with - args = [ UInt64 "count"; UInt64 "offset"; - Closure extent_closure; Closure completion_closure ]; - optargs = [ OFlags ("flags", cmd_flags) ]; + args = [ UInt64 "count"; UInt64 "offset"; Closure extent_closure ]; + optargs = [ OClosure completion_closure; OFlags ("flags", cmd_flags) ]; ret = RInt64; permitted_states = [ Connected ]; shortdesc = "send block status command to the NBD server, with callback on completion"; diff --git a/ocaml/examples/asynch_copy.ml b/ocaml/examples/asynch_copy.ml index 7dbe976..5aa6e60 100644 --- a/ocaml/examples/asynch_copy.ml +++ b/ocaml/examples/asynch_copy.ml @@ -49,7 +49,7 @@ let asynch_copy src dst = let bs = min bs (size -^ !soff) in let buf = NBD.Buffer.alloc (Int64.to_int bs) in ignore (NBD.aio_pread_callback src buf !soff - (read_completed buf !soff)); + ~completion:(read_completed buf !soff)); soff := !soff +^ bs ); @@ -59,7 +59,8 @@ let asynch_copy src dst = List.iter ( fun (buf, offset) -> (* Note the size of the write is implicitly stored in buf. *) - ignore (NBD.aio_pwrite_callback dst buf offset (write_completed buf)) + ignore (NBD.aio_pwrite_callback dst buf offset + ~completion:(write_completed buf)) ) !writes; writes := []; diff --git a/ocaml/tests/test_505_aio_pread_structured_callback.ml b/ocaml/tests/test_505_aio_pread_structured_callback.ml index 9b9ac2c..dc0d557 100644 --- a/ocaml/tests/test_505_aio_pread_structured_callback.ml +++ b/ocaml/tests/test_505_aio_pread_structured_callback.ml @@ -60,7 +60,8 @@ let () = (* First try: succeed in both callbacks *) let buf = NBD.Buffer.alloc 512 in - let cookie = NBD.aio_pread_structured_callback nbd buf 0_L (chunk 42) (callback 42) in + let cookie = NBD.aio_pread_structured_callback nbd buf 0_L (chunk 42) + ~completion:(callback 42) in while not (NBD.aio_command_completed nbd cookie) do ignore (NBD.poll nbd (-1)) done; @@ -71,7 +72,8 @@ let () = (* Second try: fail only during callback *) let buf = NBD.Buffer.alloc 512 in - let cookie = NBD.aio_pread_structured_callback nbd buf 0_L (chunk 42) (callback 43) in + let cookie = NBD.aio_pread_structured_callback nbd buf 0_L (chunk 42) + ~completion:(callback 43) in try while not (NBD.aio_command_completed nbd cookie) do ignore (NBD.poll nbd (-1)) @@ -84,7 +86,8 @@ let () = (* Third try: fail during both *) let buf = NBD.Buffer.alloc 512 in - let cookie = NBD.aio_pread_structured_callback nbd buf 0_L (chunk 43) (callback 44) in + let cookie = NBD.aio_pread_structured_callback nbd buf 0_L (chunk 43) + ~completion:(callback 44) in try while not (NBD.aio_command_completed nbd cookie) do ignore (NBD.poll nbd (-1)) @@ -97,7 +100,8 @@ let () = (* Fourth try: fail only during chunk *) let buf = NBD.Buffer.alloc 512 in - let cookie = NBD.aio_pread_structured_callback nbd buf 0_L (chunk 43) (callback 42) in + let cookie = NBD.aio_pread_structured_callback nbd buf 0_L (chunk 43) + ~completion:(callback 42) in try while not (NBD.aio_command_completed nbd cookie) do ignore (NBD.poll nbd (-1)) diff --git a/ocaml/tests/test_590_aio_copy.ml b/ocaml/tests/test_590_aio_copy.ml index 290ca93..18ce389 100644 --- a/ocaml/tests/test_590_aio_copy.ml +++ b/ocaml/tests/test_590_aio_copy.ml @@ -72,7 +72,7 @@ let asynch_copy src dst = let bs = min bs (size -^ !soff) in let buf = NBD.Buffer.alloc (Int64.to_int bs) in ignore (NBD.aio_pread_callback src buf !soff - (read_completed buf !soff)); + ~completion:(read_completed buf !soff)); soff := !soff +^ bs ); @@ -82,7 +82,8 @@ let asynch_copy src dst = List.iter ( fun (buf, offset) -> (* Note the size of the write is implicitly stored in buf. *) - ignore (NBD.aio_pwrite_callback dst buf offset (write_completed buf)) + ignore (NBD.aio_pwrite_callback dst buf offset + ~completion:(write_completed buf)) ) !writes; writes := []; -- 2.22.0

Commit 0904dd113dfa36485623b3c1756dc1aeab3dddeb removed the theoretical possibility of clearing the debug callback from the handle by setting it to NULL (although that was dubious from an API point of view). This commit adds an explicit way to do this. Another advantage of this is we can internally call this API from other places when we want to clear/free the debug callback. --- generator/generator | 11 +++++++++++ lib/debug.c | 17 ++++++++++++++--- lib/handle.c | 4 +--- 3 files changed, 26 insertions(+), 6 deletions(-) diff --git a/generator/generator b/generator/generator index 6ccfc5f..d76eeea 100755 --- a/generator/generator +++ b/generator/generator @@ -1013,6 +1013,17 @@ a handle then messages are printed on C<stderr>. The callback should not call C<nbd_*> APIs on the same handle since it can be called while holding the handle lock and will cause a deadlock."; +}; + + "clear_debug_callback", { + default_call with + args = []; + ret = RErr; + shortdesc = "clear the debug callback"; + longdesc = "\ +Remove the debug callback if one was previously associated +with the handle (with C<nbd_set_debug_callback>). If not +callback was associated this does nothing."; }; "set_handle_name", { diff --git a/lib/debug.c b/lib/debug.c index ad4d9cb..c1decb2 100644 --- a/lib/debug.c +++ b/lib/debug.c @@ -38,13 +38,24 @@ nbd_unlocked_get_debug (struct nbd_handle *h) return h->debug; } +int +nbd_unlocked_clear_debug_callback (struct nbd_handle *h) +{ + if (h->debug_callback) + /* ignore return value */ + h->debug_callback (LIBNBD_CALLBACK_FREE, h->debug_data, NULL, NULL); + h->debug_callback = NULL; + h->debug_data = NULL; + return 0; +} + int nbd_unlocked_set_debug_callback (struct nbd_handle *h, nbd_debug_callback debug_callback, void *data) { - if (h->debug_callback) - /* ignore return value */ - h->debug_callback (LIBNBD_CALLBACK_FREE, h->debug_data, NULL, NULL); + /* This can't fail at the moment - see implementation above. */ + nbd_unlocked_clear_debug_callback (h); + h->debug_callback = debug_callback; h->debug_data = data; return 0; diff --git a/lib/handle.c b/lib/handle.c index 054c8a7..d599eef 100644 --- a/lib/handle.c +++ b/lib/handle.c @@ -113,9 +113,7 @@ nbd_close (struct nbd_handle *h) return; /* Free user callbacks first. */ - if (h->debug_callback) - h->debug_callback (LIBNBD_CALLBACK_FREE, h->debug_data, NULL, NULL); - h->debug_callback = NULL; + nbd_unlocked_clear_debug_callback (h); free (h->bs_entries); for (m = h->meta_contexts; m != NULL; m = m_next) { -- 2.22.0

On Tue, Aug 13, 2019 at 10:41:27AM -0500, Eric Blake wrote: Yes this can never fail. We don't have a way to say that (except RUInt but that's a bit different), and I'm a bit dubious about adding one because it limits our choices in future. Oops, fixed in my copy. I think it's probably best to return 0 always. Reduces complexity for callers if they don't have to worry if a debug function was previously registered or not. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org