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scripts: add block-coroutine-wrapper.py
We have a very frequent pattern of creating a coroutine from a function with several arguments: - create a structure to pack parameters - create _entry function to call original function taking parameters from struct - do different magic to handle completion: set ret to NOT_DONE or EINPROGRESS or use separate bool field - fill the struct and create coroutine from _entry function with this struct as a parameter - do coroutine enter and BDRV_POLL_WHILE loop Let's reduce code duplication by generating coroutine wrappers. This patch adds scripts/block-coroutine-wrapper.py together with some friends, which will generate functions with declared prototypes marked by the 'generated_co_wrapper' specifier. The usage of new code generation is as follows: 1. define the coroutine function somewhere int coroutine_fn bdrv_co_NAME(...) {...} 2. declare in some header file int generated_co_wrapper bdrv_NAME(...); with same list of parameters (generated_co_wrapper is defined in "include/block/block.h"). 3. Make sure the block_gen_c declaration in block/meson.build mentions the file with your marker function. Still, no function is now marked, this work is for the following commit. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-Id: <20200924185414.28642-5-vsementsov@virtuozzo.com> [Added encoding='utf-8' to open() calls as requested by Vladimir. Fixed typo and grammar issues pointed out by Eric Blake. Removed clang-format dependency that caused build test issues. --Stefan] Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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/* | ||
* Block coroutine wrapping core, used by auto-generated block/block-gen.c | ||
* | ||
* Copyright (c) 2003 Fabrice Bellard | ||
* Copyright (c) 2020 Virtuozzo International GmbH | ||
* | ||
* Permission is hereby granted, free of charge, to any person obtaining a copy | ||
* of this software and associated documentation files (the "Software"), to deal | ||
* in the Software without restriction, including without limitation the rights | ||
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
* copies of the Software, and to permit persons to whom the Software is | ||
* furnished to do so, subject to the following conditions: | ||
* | ||
* The above copyright notice and this permission notice shall be included in | ||
* all copies or substantial portions of the Software. | ||
* | ||
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL | ||
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
* THE SOFTWARE. | ||
*/ | ||
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#ifndef BLOCK_BLOCK_GEN_H | ||
#define BLOCK_BLOCK_GEN_H | ||
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#include "block/block_int.h" | ||
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/* Base structure for argument packing structures */ | ||
typedef struct BdrvPollCo { | ||
BlockDriverState *bs; | ||
bool in_progress; | ||
int ret; | ||
Coroutine *co; /* Keep pointer here for debugging */ | ||
} BdrvPollCo; | ||
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static inline int bdrv_poll_co(BdrvPollCo *s) | ||
{ | ||
assert(!qemu_in_coroutine()); | ||
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bdrv_coroutine_enter(s->bs, s->co); | ||
BDRV_POLL_WHILE(s->bs, s->in_progress); | ||
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return s->ret; | ||
} | ||
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#endif /* BLOCK_BLOCK_GEN_H */ |
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======================= | ||
block-coroutine-wrapper | ||
======================= | ||
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A lot of functions in QEMU block layer (see ``block/*``) can only be | ||
called in coroutine context. Such functions are normally marked by the | ||
coroutine_fn specifier. Still, sometimes we need to call them from | ||
non-coroutine context; for this we need to start a coroutine, run the | ||
needed function from it and wait for the coroutine to finish in a | ||
BDRV_POLL_WHILE() loop. To run a coroutine we need a function with one | ||
void* argument. So for each coroutine_fn function which needs a | ||
non-coroutine interface, we should define a structure to pack the | ||
parameters, define a separate function to unpack the parameters and | ||
call the original function and finally define a new interface function | ||
with same list of arguments as original one, which will pack the | ||
parameters into a struct, create a coroutine, run it and wait in | ||
BDRV_POLL_WHILE() loop. It's boring to create such wrappers by hand, | ||
so we have a script to generate them. | ||
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Usage | ||
===== | ||
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Assume we have defined the ``coroutine_fn`` function | ||
``bdrv_co_foo(<some args>)`` and need a non-coroutine interface for it, | ||
called ``bdrv_foo(<same args>)``. In this case the script can help. To | ||
trigger the generation: | ||
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1. You need ``bdrv_foo`` declaration somewhere (for example, in | ||
``block/coroutines.h``) with the ``generated_co_wrapper`` mark, | ||
like this: | ||
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.. code-block:: c | ||
int generated_co_wrapper bdrv_foo(<some args>); | ||
2. You need to feed this declaration to block-coroutine-wrapper script. | ||
For this, add the .h (or .c) file with the declaration to the | ||
``input: files(...)`` list of ``block_gen_c`` target declaration in | ||
``block/meson.build`` | ||
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You are done. During the build, coroutine wrappers will be generated in | ||
``<BUILD_DIR>/block/block-gen.c``. | ||
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Links | ||
===== | ||
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1. The script location is ``scripts/block-coroutine-wrapper.py``. | ||
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2. Generic place for private ``generated_co_wrapper`` declarations is | ||
``block/coroutines.h``, for public declarations: | ||
``include/block/block.h`` | ||
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3. The core API of generated coroutine wrappers is placed in | ||
(not generated) ``block/block-gen.h`` |
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@@ -32,3 +32,4 @@ Contents: | |
s390-dasd-ipl | ||
clocks | ||
qom | ||
block-coroutine-wrapper |
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#! /usr/bin/env python3 | ||
"""Generate coroutine wrappers for block subsystem. | ||
The program parses one or several concatenated c files from stdin, | ||
searches for functions with the 'generated_co_wrapper' specifier | ||
and generates corresponding wrappers on stdout. | ||
Usage: block-coroutine-wrapper.py generated-file.c FILE.[ch]... | ||
Copyright (c) 2020 Virtuozzo International GmbH. | ||
This program is free software; you can redistribute it and/or modify | ||
it under the terms of the GNU General Public License as published by | ||
the Free Software Foundation; either version 2 of the License, or | ||
(at your option) any later version. | ||
This program is distributed in the hope that it will be useful, | ||
but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
GNU General Public License for more details. | ||
You should have received a copy of the GNU General Public License | ||
along with this program. If not, see <http://www.gnu.org/licenses/>. | ||
""" | ||
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import sys | ||
import re | ||
from typing import Iterator | ||
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def gen_header(): | ||
copyright = re.sub('^.*Copyright', 'Copyright', __doc__, flags=re.DOTALL) | ||
copyright = re.sub('^(?=.)', ' * ', copyright.strip(), flags=re.MULTILINE) | ||
copyright = re.sub('^$', ' *', copyright, flags=re.MULTILINE) | ||
return f"""\ | ||
/* | ||
* File is generated by scripts/block-coroutine-wrapper.py | ||
* | ||
{copyright} | ||
*/ | ||
#include "qemu/osdep.h" | ||
#include "block/coroutines.h" | ||
#include "block/block-gen.h" | ||
#include "block/block_int.h"\ | ||
""" | ||
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class ParamDecl: | ||
param_re = re.compile(r'(?P<decl>' | ||
r'(?P<type>.*[ *])' | ||
r'(?P<name>[a-z][a-z0-9_]*)' | ||
r')') | ||
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def __init__(self, param_decl: str) -> None: | ||
m = self.param_re.match(param_decl.strip()) | ||
if m is None: | ||
raise ValueError(f'Wrong parameter declaration: "{param_decl}"') | ||
self.decl = m.group('decl') | ||
self.type = m.group('type') | ||
self.name = m.group('name') | ||
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class FuncDecl: | ||
def __init__(self, return_type: str, name: str, args: str) -> None: | ||
self.return_type = return_type.strip() | ||
self.name = name.strip() | ||
self.args = [ParamDecl(arg.strip()) for arg in args.split(',')] | ||
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def gen_list(self, format: str) -> str: | ||
return ', '.join(format.format_map(arg.__dict__) for arg in self.args) | ||
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def gen_block(self, format: str) -> str: | ||
return '\n'.join(format.format_map(arg.__dict__) for arg in self.args) | ||
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# Match wrappers declared with a generated_co_wrapper mark | ||
func_decl_re = re.compile(r'^int\s*generated_co_wrapper\s*' | ||
r'(?P<wrapper_name>[a-z][a-z0-9_]*)' | ||
r'\((?P<args>[^)]*)\);$', re.MULTILINE) | ||
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def func_decl_iter(text: str) -> Iterator: | ||
for m in func_decl_re.finditer(text): | ||
yield FuncDecl(return_type='int', | ||
name=m.group('wrapper_name'), | ||
args=m.group('args')) | ||
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def snake_to_camel(func_name: str) -> str: | ||
""" | ||
Convert underscore names like 'some_function_name' to camel-case like | ||
'SomeFunctionName' | ||
""" | ||
words = func_name.split('_') | ||
words = [w[0].upper() + w[1:] for w in words] | ||
return ''.join(words) | ||
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def gen_wrapper(func: FuncDecl) -> str: | ||
assert func.name.startswith('bdrv_') | ||
assert not func.name.startswith('bdrv_co_') | ||
assert func.return_type == 'int' | ||
assert func.args[0].type in ['BlockDriverState *', 'BdrvChild *'] | ||
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name = 'bdrv_co_' + func.name[5:] | ||
bs = 'bs' if func.args[0].type == 'BlockDriverState *' else 'child->bs' | ||
struct_name = snake_to_camel(name) | ||
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return f"""\ | ||
/* | ||
* Wrappers for {name} | ||
*/ | ||
typedef struct {struct_name} {{ | ||
BdrvPollCo poll_state; | ||
{ func.gen_block(' {decl};') } | ||
}} {struct_name}; | ||
static void coroutine_fn {name}_entry(void *opaque) | ||
{{ | ||
{struct_name} *s = opaque; | ||
s->poll_state.ret = {name}({ func.gen_list('s->{name}') }); | ||
s->poll_state.in_progress = false; | ||
aio_wait_kick(); | ||
}} | ||
int {func.name}({ func.gen_list('{decl}') }) | ||
{{ | ||
if (qemu_in_coroutine()) {{ | ||
return {name}({ func.gen_list('{name}') }); | ||
}} else {{ | ||
{struct_name} s = {{ | ||
.poll_state.bs = {bs}, | ||
.poll_state.in_progress = true, | ||
{ func.gen_block(' .{name} = {name},') } | ||
}}; | ||
s.poll_state.co = qemu_coroutine_create({name}_entry, &s); | ||
return bdrv_poll_co(&s.poll_state); | ||
}} | ||
}}""" | ||
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def gen_wrappers(input_code: str) -> str: | ||
res = '' | ||
for func in func_decl_iter(input_code): | ||
res += '\n\n\n' | ||
res += gen_wrapper(func) | ||
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return res | ||
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if __name__ == '__main__': | ||
if len(sys.argv) < 3: | ||
exit(f'Usage: {sys.argv[0]} OUT_FILE.c IN_FILE.[ch]...') | ||
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with open(sys.argv[1], 'w', encoding='utf-8') as f_out: | ||
f_out.write(gen_header()) | ||
for fname in sys.argv[2:]: | ||
with open(fname, encoding='utf-8') as f_in: | ||
f_out.write(gen_wrappers(f_in.read())) | ||
f_out.write('\n') |