[v8,4/7] scripts: add block-coroutine-wrapper.py

We have a very frequent pattern of creating coroutine from function
with several arguments:

  - create 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 and 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 'generated_co_wrapper' specifier.

The usage of new code generation is as follows:

    1. define somewhere

        int coroutine_fn bdrv_co_NAME(...) {...}

       function

    2. declare in some header file

        int generated_co_wrapper bdrv_NAME(...);

       function with same list of parameters. (you'll need to include
       "block/generated-co-wrapper.h" to get the specifier)

    3. both declarations should be available through block/coroutines.h
       header.

    4. add header with generated_co_wrapper declaration into
       COROUTINE_HEADERS list in Makefile

Still, no function is now marked, this work is for the following
commit.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 docs/devel/block-coroutine-wrapper.rst |  54 +++++++
 block/block-gen.h                      |  49 +++++++
 include/block/block.h                  |  10 ++
 block/meson.build                      |   8 ++
 scripts/block-coroutine-wrapper.py     | 187 +++++++++++++++++++++++++
 5 files changed, 308 insertions(+)
 create mode 100644 docs/devel/block-coroutine-wrapper.rst
 create mode 100644 block/block-gen.h
 create mode 100755 scripts/block-coroutine-wrapper.py

15.09.2020 19:44, Vladimir Sementsov-Ogievskiy wrote:
> We have a very frequent pattern of creating coroutine from function
> with several arguments:
> 
>    - create 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 and 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 'generated_co_wrapper' specifier.
> 
> The usage of new code generation is as follows:
> 
>      1. define somewhere
> 
>          int coroutine_fn bdrv_co_NAME(...) {...}
> 
>         function
> 
>      2. declare in some header file
> 
>          int generated_co_wrapper bdrv_NAME(...);
> 
>         function with same list of parameters. (you'll need to include
>         "block/generated-co-wrapper.h" to get the specifier)
> 
>      3. both declarations should be available through block/coroutines.h
>         header.
> 
>      4. add header with generated_co_wrapper declaration into
>         COROUTINE_HEADERS list in Makefile
> 
> Still, no function is now marked, this work is for the following
> commit.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy<vsementsov@virtuozzo.com>
> ---
>   docs/devel/block-coroutine-wrapper.rst |  54 +++++++
>   block/block-gen.h                      |  49 +++++++
>   include/block/block.h                  |  10 ++
>   block/meson.build                      |   8 ++
>   scripts/block-coroutine-wrapper.py     | 187 +++++++++++++++++++++++++
>   5 files changed, 308 insertions(+)
>   create mode 100644 docs/devel/block-coroutine-wrapper.rst
>   create mode 100644 block/block-gen.h
>   create mode 100755 scripts/block-coroutine-wrapper.py


Also needed:

diff --git a/docs/devel/index.rst b/docs/devel/index.rst
index 04773ce076..cb0abe1e69 100644
--- a/docs/devel/index.rst
+++ b/docs/devel/index.rst
@@ -31,3 +31,4 @@ Contents:
     reset
     s390-dasd-ipl
     clocks
+   block-coroutine-wrapper

On 9/15/20 3:02 PM, Vladimir Sementsov-Ogievskiy wrote:
> 15.09.2020 19:44, Vladimir Sementsov-Ogievskiy wrote:
>> We have a very frequent pattern of creating coroutine from function
>> with several arguments:
>>
>>    - create 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 and 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 'generated_co_wrapper' specifier.
>>

>>
>>      4. add header with generated_co_wrapper declaration into
>>         COROUTINE_HEADERS list in Makefile

This phrase is out-of-date.  I also see 4 steps here,...

>>
>> Still, no function is now marked, this work is for the following
>> commit.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy<vsementsov@virtuozzo.com>
>> ---
>>   docs/devel/block-coroutine-wrapper.rst |  54 +++++++
>>   block/block-gen.h                      |  49 +++++++
>>   include/block/block.h                  |  10 ++
>>   block/meson.build                      |   8 ++
>>   scripts/block-coroutine-wrapper.py     | 187 +++++++++++++++++++++++++
>>   5 files changed, 308 insertions(+)
>>   create mode 100644 docs/devel/block-coroutine-wrapper.rst
>>   create mode 100644 block/block-gen.h
>>   create mode 100755 scripts/block-coroutine-wrapper.py
> 
> 
> Also needed:
> 
> diff --git a/docs/devel/index.rst b/docs/devel/index.rst
> index 04773ce076..cb0abe1e69 100644
> --- a/docs/devel/index.rst
> +++ b/docs/devel/index.rst
> @@ -31,3 +31,4 @@ Contents:
>      reset
>      s390-dasd-ipl
>      clocks
> +   block-coroutine-wrapper

I've squashed that in.

> +++ b/docs/devel/block-coroutine-wrapper.rst
> @@ -0,0 +1,54 @@
> +=======================
> +block-coroutine-wrapper
> +=======================
> +
> +A lot of functions in QEMJ block layer (see ``block/*``) can by called

QEMU

s/by called only/only be called/

> +only in coroutine context. Such functions are normally marked by

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


s/context,/context;/

> +needed function from it and wait for coroutine finish in

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

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.
> 
> +Usage
> +=====
> +
> +Assume we have defined ``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:
> +
> +1. You need ``bdrv_foo`` declaration somewhere (for example in
> +   ``block/coroutines.h`` with ``generated_co_wrapper`` mark,
> +   like this:

Missing a closing ).

> +
> +.. code-block:: c
> +
> +    int generated_co_wrapper bdrv_foor(<some args>);

s/foor/foo/

> +
> +2. You need to feed this declaration to block-coroutine-wrapper script.

to the block-

> +   For this, add .h (or .c) file with the declaration to
> +   ``input: files(...)`` list of ``block_gen_c`` target declaration in
> +   ``block/meson.build``
> +
> +You are done. On build, coroutine wrappers will be generated in

s/On/During the/

> +``<BUILD_DIR>/block/block-gen.c``.

...but 2 in the .rst.  Presumably, the .rst steps belong in the commit 
message as well.

> +++ b/block/block-gen.h

> +++ b/include/block/block.h
> @@ -10,6 +10,16 @@
>  #include "block/blockjob.h"
>  #include "qemu/hbitmap.h"
>  
> +/*
> + * generated_co_wrapper
> + *
> + * Function specifier, which does nothing but marking functions to be

s/marking/mark/

> + * generated by scripts/block-coroutine-wrapper.py
> + *
> + * Read more in docs/devel/block-coroutine-wrapper.rst
> + */
> +#define generated_co_wrapper
> +
>  /* block.c */
>  typedef struct BlockDriver BlockDriver;
>  typedef struct BdrvChild BdrvChild;
> diff --git a/block/meson.build b/block/meson.build
> index a3e56b7cd1..88ad73583a 100644
> --- a/block/meson.build
> +++ b/block/meson.build
> @@ -107,6 +107,14 @@ module_block_h = custom_target('module_block.h',
>                                 command: [module_block_py, '@OUTPUT0@', modsrc])
>  block_ss.add(module_block_h)
>  
> +wrapper_py = find_program('../scripts/block-coroutine-wrapper.py')
> +block_gen_c = custom_target('block-gen.c',
> +                            output: 'block-gen.c',
> +                            input: files('../include/block/block.h',
> +                                         'coroutines.h'),
> +                            command: [wrapper_py, '@OUTPUT@', '@INPUT@'])
> +block_ss.add(block_gen_c)
> +
>  block_ss.add(files('stream.c'))

I tested that this works (I'm not a meson expert, but if it works, your 
patch can't be too far off ;)

>  
>  softmmu_ss.add(files('qapi-sysemu.c'))
> diff --git a/scripts/block-coroutine-wrapper.py b/scripts/block-coroutine-wrapper.py
> new file mode 100755
> index 0000000000..d859c07a5f
> --- /dev/null
> +++ b/scripts/block-coroutine-wrapper.py
> @@ -0,0 +1,187 @@
> +#!/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 'generated_co_wrapper' specifier

with the

> +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/>.
> +"""

John had a patch that unified how copyrights are (or are not) placed in 
doc comments.  I'm of the opinion that it may be easier to apply this 
patch as written and let him touch it up later, rather than forcing it 
to delay longer waiting for his style patches to land first, but I'm 
open to discussion on alternate approaches.

> +
> +import sys
> +import re
> +import subprocess
> +import json
> +from typing import Iterator
> +
> +
> +def prettify(code: str) -> str:
> +    """Prettify code using clang-format if available"""

Nothing else in the codebase uses clang-format, yet.  Is this an 
optional dependency we should be documenting somewhere?

> +
> +    try:
> +        style = json.dumps({
> +            'IndentWidth': 4,
> +            'BraceWrapping': {'AfterFunction': True},
> +            'BreakBeforeBraces': 'Custom',
> +            'SortIncludes': False,
> +            'MaxEmptyLinesToKeep': 2
> +        })

Is it worth always using a trailing comma, so that future additions 
don't have as many lines to touch?

> +        p = subprocess.run(['clang-format', f'-style={style}'], check=True,
> +                           encoding='utf-8', input=code,
> +                           stdout=subprocess.PIPE)
> +        return p.stdout
> +    except FileNotFoundError:
> +        return code
> +
> +
> +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"\
> +"""
> +
> +
> +class ParamDecl:
> +    param_re = re.compile(r'(?P<decl>'
> +                          r'(?P<type>.*[ *])'
> +                          r'(?P<name>[a-z][a-z0-9_]*)'
> +                          r')')
> +
> +    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')
> +
> +
> +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(',')]
> +
> +    def gen_list(self, format: str) -> str:
> +        return ', '.join(format.format_map(arg.__dict__) for arg in self.args)
> +
> +    def gen_block(self, format: str) -> str:
> +        return '\n'.join(format.format_map(arg.__dict__) for arg in self.args)
> +
> +
> +# 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)
> +
> +
> +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'))
> +
> +
> +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)
> +
> +
> +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 *']
> +
> +    name = 'bdrv_co_' + func.name[5:]
> +    bs = 'bs' if func.args[0].type == 'BlockDriverState *' else 'child->bs'
> +    struct_name = snake_to_camel(name)
> +
> +    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}') });

Excuse my lack of python style awareness, but why are we mixing 
{nospace} and { space } on the same line?

> +    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);
> +    }}
> +}}"""
> +
> +
> +def gen_wrappers_file(input_code: str) -> str:
> +    res = gen_header()
> +    for func in func_decl_iter(input_code):
> +        res += '\n\n\n'
> +        res += gen_wrapper(func)
> +
> +    return prettify(res)  # prettify to wrap long lines
> +
> +
> +if __name__ == '__main__':
> +    if len(sys.argv) < 3:
> +        exit(f'Usage: {sys.argv[0]} OUT_FILE.c IN_FILE.[ch]...')
> +
> +    with open(sys.argv[1], 'w') as f_out:
> +        for fname in sys.argv[2:]:
> +            with open(fname) as f_in:
> +                f_out.write(gen_wrappers_file(f_in.read()))
> +                f_out.write('\n')

Tested-by: Eric Blake <eblake@redhat.com>

There's enough grammar fixes, and the fact that John is working on 
python cleanups, to make me wonder if we need a v9, or if I should just 
stage it where it is with any other cleanups as followups.  But I'm 
liking the reduced maintenance burden once it is in, and don't want to 
drag it out to the point that it needs more rebasing as other things 
land first.

On 9/15/20 11:44 AM, Vladimir Sementsov-Ogievskiy wrote:
> We have a very frequent pattern of creating coroutine from function
> with several arguments:
> 

> +++ b/scripts/block-coroutine-wrapper.py
> @@ -0,0 +1,187 @@
> +#!/usr/bin/env python3
> +"""Generate coroutine wrappers for block subsystem.

Looking at the generated file after patch 5 is applied,...


> +
> +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"""\

This generated comment...


> +
> +
> +def gen_wrappers_file(input_code: str) -> str:
> +    res = gen_header()

...is getting inserted into the generated file...

> +    for func in func_decl_iter(input_code):
> +        res += '\n\n\n'
> +        res += gen_wrapper(func)
> +
> +    return prettify(res)  # prettify to wrap long lines
> +
> +
> +if __name__ == '__main__':
> +    if len(sys.argv) < 3:
> +        exit(f'Usage: {sys.argv[0]} OUT_FILE.c IN_FILE.[ch]...')
> +
> +    with open(sys.argv[1], 'w') as f_out:
> +        for fname in sys.argv[2:]:
> +            with open(fname) as f_in:
> +                f_out.write(gen_wrappers_file(f_in.read()))

multiple times.  You'll want to hoist the call to gen_header outside the 
loop over fname in sys.argv[2:].

On 9/23/20 7:00 PM, Eric Blake wrote:

> 
> Tested-by: Eric Blake <eblake@redhat.com>
> 
> There's enough grammar fixes, and the fact that John is working on 
> python cleanups, to make me wonder if we need a v9, or if I should just 
> stage it where it is with any other cleanups as followups.  But I'm 
> liking the reduced maintenance burden once it is in, and don't want to 
> drag it out to the point that it needs more rebasing as other things 
> land first.
> 

Here's what I've squashed in and temporarily pushed to my tree if you 
want to double-check my rebase work:
https://repo.or.cz/qemu/ericb.git/shortlog/refs/heads/master

diff --git a/docs/devel/block-coroutine-wrapper.rst 
b/docs/devel/block-coroutine-wrapper.rst
index f7050bbc8fa6..d09fff2cc539 100644
--- a/docs/devel/block-coroutine-wrapper.rst
+++ b/docs/devel/block-coroutine-wrapper.rst
@@ -2,43 +2,43 @@
  block-coroutine-wrapper
  =======================

-A lot of functions in QEMJ block layer (see ``block/*``) can by called
-only in coroutine context. Such functions are normally marked by
+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
+non-coroutine context; for this we need to start a coroutine, run the
  needed function from it and wait for coroutine finish in
  BDRV_POLL_WHILE() loop. To run a coroutine we need a function with one
-void* argument. So for each coroutine_fn function, which needs
+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.
+BDRV_POLL_WHILE() loop. It's boring to create such wrappers by hand,
+so we have a script to generate them.

  Usage
  =====

-Assume we have defined ``coroutine_fn`` function
+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:

-1. You need ``bdrv_foo`` declaration somewhere (for example in
-   ``block/coroutines.h`` with ``generated_co_wrapper`` mark,
+1. You need ``bdrv_foo`` declaration somewhere (for example, in
+   ``block/coroutines.h``) with the ``generated_co_wrapper`` mark,
     like this:

  .. code-block:: c

-    int generated_co_wrapper bdrv_foor(<some args>);
+    int generated_co_wrapper bdrv_foo(<some args>);

  2. You need to feed this declaration to block-coroutine-wrapper script.
-   For this, add .h (or .c) file with the declaration to
+   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``

-You are done. On build, coroutine wrappers will be generated in
+You are done. During the build, coroutine wrappers will be generated in
  ``<BUILD_DIR>/block/block-gen.c``.

  Links
diff --git a/docs/devel/index.rst b/docs/devel/index.rst
index 04773ce076b3..cb0abe1e6988 100644
--- a/docs/devel/index.rst
+++ b/docs/devel/index.rst
@@ -31,3 +31,4 @@ Contents:
     reset
     s390-dasd-ipl
     clocks
+   block-coroutine-wrapper
diff --git a/scripts/block-coroutine-wrapper.py 
b/scripts/block-coroutine-wrapper.py
index d859c07a5f55..8c0a08d9b020 100755
--- a/scripts/block-coroutine-wrapper.py
+++ b/scripts/block-coroutine-wrapper.py
@@ -2,7 +2,7 @@
  """Generate coroutine wrappers for block subsystem.

  The program parses one or several concatenated c files from stdin,
-searches for functions with 'generated_co_wrapper' specifier
+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]...
@@ -39,7 +39,7 @@ def prettify(code: str) -> str:
              'BraceWrapping': {'AfterFunction': True},
              'BreakBeforeBraces': 'Custom',
              'SortIncludes': False,
-            'MaxEmptyLinesToKeep': 2
+            'MaxEmptyLinesToKeep': 2,
          })
          p = subprocess.run(['clang-format', f'-style={style}'], 
check=True,
                             encoding='utf-8', input=code,
@@ -168,7 +168,7 @@ int {func.name}({ func.gen_list('{decl}') })


  def gen_wrappers_file(input_code: str) -> str:
-    res = gen_header()
+    res = ''
      for func in func_decl_iter(input_code):
          res += '\n\n\n'
          res += gen_wrapper(func)
@@ -181,6 +181,7 @@ if __name__ == '__main__':
          exit(f'Usage: {sys.argv[0]} OUT_FILE.c IN_FILE.[ch]...')

      with open(sys.argv[1], 'w') as f_out:
+        f_out.write(gen_header())
          for fname in sys.argv[2:]:
              with open(fname) as f_in:
                  f_out.write(gen_wrappers_file(f_in.read()))
diff --git a/include/block/block.h b/include/block/block.h
index d861883b8d9e..0f0ddc51b49e 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -13,7 +13,7 @@
  /*
   * generated_co_wrapper
   *
- * Function specifier, which does nothing but marking functions to be
+ * Function specifier, which does nothing but mark functions to be
   * generated by scripts/block-coroutine-wrapper.py
   *
   * Read more in docs/devel/block-coroutine-wrapper.rst

24.09.2020 03:00, Eric Blake wrote:
> On 9/15/20 3:02 PM, Vladimir Sementsov-Ogievskiy wrote:
>> 15.09.2020 19:44, Vladimir Sementsov-Ogievskiy wrote:
>>> We have a very frequent pattern of creating coroutine from function
>>> with several arguments:
>>>
>>>    - create 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 and 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 'generated_co_wrapper' specifier.
>>>
> 
>>>
>>>      4. add header with generated_co_wrapper declaration into
>>>         COROUTINE_HEADERS list in Makefile
> 
> This phrase is out-of-date.  I also see 4 steps here,...
> 
>>>
>>> Still, no function is now marked, this work is for the following
>>> commit.
>>>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy<vsementsov@virtuozzo.com>
>>> ---
>>>   docs/devel/block-coroutine-wrapper.rst |  54 +++++++
>>>   block/block-gen.h                      |  49 +++++++
>>>   include/block/block.h                  |  10 ++
>>>   block/meson.build                      |   8 ++
>>>   scripts/block-coroutine-wrapper.py     | 187 +++++++++++++++++++++++++
>>>   5 files changed, 308 insertions(+)
>>>   create mode 100644 docs/devel/block-coroutine-wrapper.rst
>>>   create mode 100644 block/block-gen.h
>>>   create mode 100755 scripts/block-coroutine-wrapper.py
>>
>>
>> Also needed:
>>
>> diff --git a/docs/devel/index.rst b/docs/devel/index.rst
>> index 04773ce076..cb0abe1e69 100644
>> --- a/docs/devel/index.rst
>> +++ b/docs/devel/index.rst
>> @@ -31,3 +31,4 @@ Contents:
>>      reset
>>      s390-dasd-ipl
>>      clocks
>> +   block-coroutine-wrapper
> 
> I've squashed that in.
> 
>> +++ b/docs/devel/block-coroutine-wrapper.rst
>> @@ -0,0 +1,54 @@
>> +=======================
>> +block-coroutine-wrapper
>> +=======================
>> +
>> +A lot of functions in QEMJ block layer (see ``block/*``) can by called
> 
> QEMU
> 
> s/by called only/only be called/
> 
>> +only in coroutine context. Such functions are normally marked by
> 
> 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
> 
> 
> s/context,/context;/
> 
>> +needed function from it and wait for coroutine finish in
> 
> 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
> 
> 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.
>>
>> +Usage
>> +=====
>> +
>> +Assume we have defined ``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:
>> +
>> +1. You need ``bdrv_foo`` declaration somewhere (for example in
>> +   ``block/coroutines.h`` with ``generated_co_wrapper`` mark,
>> +   like this:
> 
> Missing a closing ).
> 
>> +
>> +.. code-block:: c
>> +
>> +    int generated_co_wrapper bdrv_foor(<some args>);
> 
> s/foor/foo/
> 
>> +
>> +2. You need to feed this declaration to block-coroutine-wrapper script.
> 
> to the block-
> 
>> +   For this, add .h (or .c) file with the declaration to
>> +   ``input: files(...)`` list of ``block_gen_c`` target declaration in
>> +   ``block/meson.build``
>> +
>> +You are done. On build, coroutine wrappers will be generated in
> 
> s/On/During the/
> 
>> +``<BUILD_DIR>/block/block-gen.c``.
> 
> ...but 2 in the .rst.  Presumably, the .rst steps belong in the commit message as well.
> 
>> +++ b/block/block-gen.h
> 
>> +++ b/include/block/block.h
>> @@ -10,6 +10,16 @@
>>  #include "block/blockjob.h"
>>  #include "qemu/hbitmap.h"
>>
>> +/*
>> + * generated_co_wrapper
>> + *
>> + * Function specifier, which does nothing but marking functions to be
> 
> s/marking/mark/
> 
>> + * generated by scripts/block-coroutine-wrapper.py
>> + *
>> + * Read more in docs/devel/block-coroutine-wrapper.rst
>> + */
>> +#define generated_co_wrapper
>> +
>>  /* block.c */
>>  typedef struct BlockDriver BlockDriver;
>>  typedef struct BdrvChild BdrvChild;
>> diff --git a/block/meson.build b/block/meson.build
>> index a3e56b7cd1..88ad73583a 100644
>> --- a/block/meson.build
>> +++ b/block/meson.build
>> @@ -107,6 +107,14 @@ module_block_h = custom_target('module_block.h',
>>                                 command: [module_block_py, '@OUTPUT0@', modsrc])
>>  block_ss.add(module_block_h)
>>
>> +wrapper_py = find_program('../scripts/block-coroutine-wrapper.py')
>> +block_gen_c = custom_target('block-gen.c',
>> +                            output: 'block-gen.c',
>> +                            input: files('../include/block/block.h',
>> +                                         'coroutines.h'),
>> +                            command: [wrapper_py, '@OUTPUT@', '@INPUT@'])
>> +block_ss.add(block_gen_c)
>> +
>>  block_ss.add(files('stream.c'))
> 
> I tested that this works (I'm not a meson expert, but if it works, your patch can't be too far off ;)
> 
>>
>>  softmmu_ss.add(files('qapi-sysemu.c'))
>> diff --git a/scripts/block-coroutine-wrapper.py b/scripts/block-coroutine-wrapper.py
>> new file mode 100755
>> index 0000000000..d859c07a5f
>> --- /dev/null
>> +++ b/scripts/block-coroutine-wrapper.py
>> @@ -0,0 +1,187 @@
>> +#!/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 'generated_co_wrapper' specifier
> 
> with the
> 
>> +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/>.
>> +"""
> 
> John had a patch that unified how copyrights are (or are not) placed in doc comments.  I'm of the opinion that it may be easier to apply this patch as written and let him touch it up later, rather than forcing it to delay longer waiting for his style patches to land first, but I'm open to discussion on alternate approaches.

Here copyright is in doc string for purpose: it's used also for generated files :) Not sure how much is it correct, but it's fun.

> 
>> +
>> +import sys
>> +import re
>> +import subprocess
>> +import json
>> +from typing import Iterator
>> +
>> +
>> +def prettify(code: str) -> str:
>> +    """Prettify code using clang-format if available"""
> 
> Nothing else in the codebase uses clang-format, yet.  Is this an optional dependency we should be documenting somewhere?

Hmm at least I should note it in docs/devel/block-coroutine-wrapper.rst

> 
>> +
>> +    try:
>> +        style = json.dumps({
>> +            'IndentWidth': 4,
>> +            'BraceWrapping': {'AfterFunction': True},
>> +            'BreakBeforeBraces': 'Custom',
>> +            'SortIncludes': False,
>> +            'MaxEmptyLinesToKeep': 2
>> +        })
> 
> Is it worth always using a trailing comma, so that future additions don't have as many lines to touch?

Yes

> 
>> +        p = subprocess.run(['clang-format', f'-style={style}'], check=True,
>> +                           encoding='utf-8', input=code,
>> +                           stdout=subprocess.PIPE)
>> +        return p.stdout
>> +    except FileNotFoundError:
>> +        return code
>> +
>> +
>> +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"\
>> +"""
>> +
>> +
>> +class ParamDecl:
>> +    param_re = re.compile(r'(?P<decl>'
>> +                          r'(?P<type>.*[ *])'
>> +                          r'(?P<name>[a-z][a-z0-9_]*)'
>> +                          r')')
>> +
>> +    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')
>> +
>> +
>> +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(',')]
>> +
>> +    def gen_list(self, format: str) -> str:
>> +        return ', '.join(format.format_map(arg.__dict__) for arg in self.args)
>> +
>> +    def gen_block(self, format: str) -> str:
>> +        return '\n'.join(format.format_map(arg.__dict__) for arg in self.args)
>> +
>> +
>> +# 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)
>> +
>> +
>> +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'))
>> +
>> +
>> +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)
>> +
>> +
>> +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 *']
>> +
>> +    name = 'bdrv_co_' + func.name[5:]
>> +    bs = 'bs' if func.args[0].type == 'BlockDriverState *' else 'child->bs'
>> +    struct_name = snake_to_camel(name)
>> +
>> +    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}') });
> 
> Excuse my lack of python style awareness, but why are we mixing {nospace} and { space } on the same line?

Hmm. It's just
  - strange for me to add spaces in first case, for just one variable
  - hard to read the second case without spaces
  - strange to make exclusion for only one line (if add spaces in both cases here, we should add spaces in all cases in the file)

It seems inconsistent.. But at least I'm consistent in this mixed style:) So, I'd keep as if neither of us has strong opinion on this.

> 
>> +    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);
>> +    }}
>> +}}"""
>> +
>> +
>> +def gen_wrappers_file(input_code: str) -> str:
>> +    res = gen_header()
>> +    for func in func_decl_iter(input_code):
>> +        res += '\n\n\n'
>> +        res += gen_wrapper(func)
>> +
>> +    return prettify(res)  # prettify to wrap long lines
>> +
>> +
>> +if __name__ == '__main__':
>> +    if len(sys.argv) < 3:
>> +        exit(f'Usage: {sys.argv[0]} OUT_FILE.c IN_FILE.[ch]...')
>> +
>> +    with open(sys.argv[1], 'w') as f_out:
>> +        for fname in sys.argv[2:]:
>> +            with open(fname) as f_in:
>> +                f_out.write(gen_wrappers_file(f_in.read()))
>> +                f_out.write('\n')
> 
> Tested-by: Eric Blake <eblake@redhat.com>
> 
> There's enough grammar fixes, and the fact that John is working on python cleanups, to make me wonder if we need a v9, or if I should just stage it where it is with any other cleanups as followups.  But I'm liking the reduced maintenance burden once it is in, and don't want to drag it out to the point that it needs more rebasing as other things land first.
>

24.09.2020 03:18, Eric Blake wrote:
> On 9/15/20 11:44 AM, Vladimir Sementsov-Ogievskiy wrote:
>> We have a very frequent pattern of creating coroutine from function
>> with several arguments:
>>
> 
>> +++ b/scripts/block-coroutine-wrapper.py
>> @@ -0,0 +1,187 @@
>> +#!/usr/bin/env python3
>> +"""Generate coroutine wrappers for block subsystem.
> 
> Looking at the generated file after patch 5 is applied,...
> 
> 
>> +
>> +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"""\
> 
> This generated comment...
> 
> 
>> +
>> +
>> +def gen_wrappers_file(input_code: str) -> str:
>> +    res = gen_header()
> 
> ...is getting inserted into the generated file...
> 
>> +    for func in func_decl_iter(input_code):
>> +        res += '\n\n\n'
>> +        res += gen_wrapper(func)
>> +
>> +    return prettify(res)  # prettify to wrap long lines
>> +
>> +
>> +if __name__ == '__main__':
>> +    if len(sys.argv) < 3:
>> +        exit(f'Usage: {sys.argv[0]} OUT_FILE.c IN_FILE.[ch]...')
>> +
>> +    with open(sys.argv[1], 'w') as f_out:
>> +        for fname in sys.argv[2:]:
>> +            with open(fname) as f_in:
>> +                f_out.write(gen_wrappers_file(f_in.read()))
> 
> multiple times.  You'll want to hoist the call to gen_header outside the loop over fname in sys.argv[2:].
> 

Right, thanks for fixing. I missed it when rebasing on meson system (and move to calling gen_wrappers_file() several times). Hmm, gen_wrappers_file() is now a bit misleading name, it would better be just gen_wrappers()

24.09.2020 04:20, Eric Blake wrote:
> On 9/23/20 7:00 PM, Eric Blake wrote:
> 
>>
>> Tested-by: Eric Blake <eblake@redhat.com>
>>
>> There's enough grammar fixes, and the fact that John is working on python cleanups, to make me wonder if we need a v9, or if I should just stage it where it is with any other cleanups as followups.  But I'm liking the reduced maintenance burden once it is in, and don't want to drag it out to the point that it needs more rebasing as other things land first.
>>
> 
> Here's what I've squashed in and temporarily pushed to my tree if you want to double-check my rebase work:
> https://repo.or.cz/qemu/ericb.git/shortlog/refs/heads/master
> 
> diff --git a/docs/devel/block-coroutine-wrapper.rst b/docs/devel/block-coroutine-wrapper.rst
> index f7050bbc8fa6..d09fff2cc539 100644
> --- a/docs/devel/block-coroutine-wrapper.rst
> +++ b/docs/devel/block-coroutine-wrapper.rst
> @@ -2,43 +2,43 @@
>   block-coroutine-wrapper
>   =======================
> 
> -A lot of functions in QEMJ block layer (see ``block/*``) can by called
> -only in coroutine context. Such functions are normally marked by
> +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
> +non-coroutine context; for this we need to start a coroutine, run the
>   needed function from it and wait for coroutine finish in
>   BDRV_POLL_WHILE() loop. To run a coroutine we need a function with one
> -void* argument. So for each coroutine_fn function, which needs
> +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.
> +BDRV_POLL_WHILE() loop. It's boring to create such wrappers by hand,
> +so we have a script to generate them.
> 
>   Usage
>   =====
> 
> -Assume we have defined ``coroutine_fn`` function
> +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:
> 
> -1. You need ``bdrv_foo`` declaration somewhere (for example in
> -   ``block/coroutines.h`` with ``generated_co_wrapper`` mark,
> +1. You need ``bdrv_foo`` declaration somewhere (for example, in
> +   ``block/coroutines.h``) with the ``generated_co_wrapper`` mark,
>      like this:
> 
>   .. code-block:: c
> 
> -    int generated_co_wrapper bdrv_foor(<some args>);
> +    int generated_co_wrapper bdrv_foo(<some args>);
> 
>   2. You need to feed this declaration to block-coroutine-wrapper script.
> -   For this, add .h (or .c) file with the declaration to
> +   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``
> 
> -You are done. On build, coroutine wrappers will be generated in
> +You are done. During the build, coroutine wrappers will be generated in
>   ``<BUILD_DIR>/block/block-gen.c``.
> 
>   Links
> diff --git a/docs/devel/index.rst b/docs/devel/index.rst
> index 04773ce076b3..cb0abe1e6988 100644
> --- a/docs/devel/index.rst
> +++ b/docs/devel/index.rst
> @@ -31,3 +31,4 @@ Contents:
>      reset
>      s390-dasd-ipl
>      clocks
> +   block-coroutine-wrapper
> diff --git a/scripts/block-coroutine-wrapper.py b/scripts/block-coroutine-wrapper.py
> index d859c07a5f55..8c0a08d9b020 100755
> --- a/scripts/block-coroutine-wrapper.py
> +++ b/scripts/block-coroutine-wrapper.py
> @@ -2,7 +2,7 @@
>   """Generate coroutine wrappers for block subsystem.
> 
>   The program parses one or several concatenated c files from stdin,
> -searches for functions with 'generated_co_wrapper' specifier
> +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]...
> @@ -39,7 +39,7 @@ def prettify(code: str) -> str:
>               'BraceWrapping': {'AfterFunction': True},
>               'BreakBeforeBraces': 'Custom',
>               'SortIncludes': False,
> -            'MaxEmptyLinesToKeep': 2
> +            'MaxEmptyLinesToKeep': 2,
>           })
>           p = subprocess.run(['clang-format', f'-style={style}'], check=True,
>                              encoding='utf-8', input=code,
> @@ -168,7 +168,7 @@ int {func.name}({ func.gen_list('{decl}') })
> 
> 
>   def gen_wrappers_file(input_code: str) -> str:
> -    res = gen_header()
> +    res = ''
>       for func in func_decl_iter(input_code):
>           res += '\n\n\n'
>           res += gen_wrapper(func)
> @@ -181,6 +181,7 @@ if __name__ == '__main__':
>           exit(f'Usage: {sys.argv[0]} OUT_FILE.c IN_FILE.[ch]...')
> 
>       with open(sys.argv[1], 'w') as f_out:
> +        f_out.write(gen_header())
>           for fname in sys.argv[2:]:
>               with open(fname) as f_in:
>                   f_out.write(gen_wrappers_file(f_in.read()))
> diff --git a/include/block/block.h b/include/block/block.h
> index d861883b8d9e..0f0ddc51b49e 100644
> --- a/include/block/block.h
> +++ b/include/block/block.h
> @@ -13,7 +13,7 @@
>   /*
>    * generated_co_wrapper
>    *
> - * Function specifier, which does nothing but marking functions to be
> + * Function specifier, which does nothing but mark functions to be
>    * generated by scripts/block-coroutine-wrapper.py
>    *
>    * Read more in docs/devel/block-coroutine-wrapper.rst
> 
> 
> 


Seems OK, thanks!

On Tue, Sep 15, 2020 at 07:44:08PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>  create mode 100755 scripts/block-coroutine-wrapper.py

Please see docs/devel/build-system.rst "Support scripts" for the
preferred way of adding Python scripts to the build system. Mode should
be 644 and the interpreter line should be "#! /usr/bin/env python3"
(with the space). That way meson will run it under the configured
--python= interpreter.

> 
> diff --git a/docs/devel/block-coroutine-wrapper.rst b/docs/devel/block-coroutine-wrapper.rst
> new file mode 100644
> index 0000000000..f7050bbc8f
> --- /dev/null
> +++ b/docs/devel/block-coroutine-wrapper.rst
> @@ -0,0 +1,54 @@
> +=======================
> +block-coroutine-wrapper
> +=======================
> +
> +A lot of functions in QEMJ block layer (see ``block/*``) can by called

s/QEMJ/QEMU/

> +only in coroutine context. Such functions are normally marked by
> +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 coroutine finish in
> +BDRV_POLL_WHILE() loop. To run a coroutine we need a function with one
> +void* argument. So for each coroutine_fn function, which needs
> +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.
> +
> +Usage
> +=====
> +
> +Assume we have defined ``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:
> +
> +1. You need ``bdrv_foo`` declaration somewhere (for example in
> +   ``block/coroutines.h`` with ``generated_co_wrapper`` mark,
> +   like this:
> +
> +.. code-block:: c
> +
> +    int generated_co_wrapper bdrv_foor(<some args>);

s/foor/foo/

On 9/23/20 8:00 PM, Eric Blake wrote:
> 
> 
> There's enough grammar fixes, and the fact that John is working on 
> python cleanups, to make me wonder if we need a v9, or if I should just 
> stage it where it is with any other cleanups as followups.  But I'm 
> liking the reduced maintenance burden once it is in, and don't want to 
> drag it out to the point that it needs more rebasing as other things 
> land first.

Don't worry about it too much. I'd rather we have a helpful script 
sooner than later than worry about Python style purity before I have the 
CI mechanisms for it fully established.

(I eyeballed it and it looks like you already use type hints, so I have 
faith it won't need much cleanup.)

Thanks!

--js

On 9/15/20 11:44 AM, Vladimir Sementsov-Ogievskiy wrote:
> We have a very frequent pattern of creating coroutine from function
> with several arguments:
> 

> +++ b/docs/devel/block-coroutine-wrapper.rst
> @@ -0,0 +1,54 @@
> +=======================
> +block-coroutine-wrapper
> +=======================
> +
> +A lot of functions in QEMJ block layer (see ``block/*``) can by called

My editor italicized everhting after block/*...

> +only in coroutine context. Such functions are normally marked by
> +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 coroutine finish in
> +BDRV_POLL_WHILE() loop. To run a coroutine we need a function with one
> +void* argument. So for each coroutine_fn function, which needs

...through void*.  I wonder if you need to use \* to let .rst know that 
these are literal *, and not markup for a different font style. 
Although I did not check the actual generated docs to see how they look.

24.09.2020 20:56, Eric Blake wrote:
> On 9/15/20 11:44 AM, Vladimir Sementsov-Ogievskiy wrote:
>> We have a very frequent pattern of creating coroutine from function
>> with several arguments:
>>
> 
>> +++ b/docs/devel/block-coroutine-wrapper.rst
>> @@ -0,0 +1,54 @@
>> +=======================
>> +block-coroutine-wrapper
>> +=======================
>> +
>> +A lot of functions in QEMJ block layer (see ``block/*``) can by called
> 
> My editor italicized everhting after block/*...
> 
>> +only in coroutine context. Such functions are normally marked by
>> +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 coroutine finish in
>> +BDRV_POLL_WHILE() loop. To run a coroutine we need a function with one
>> +void* argument. So for each coroutine_fn function, which needs
> 
> ...through void*.  I wonder if you need to use \* to let .rst know that these are literal *, and not markup for a different font style. Although I did not check the actual generated docs to see how they look.
> 

Intuitively, `` should have greater priority than *.

I now check ./build/docs/devel/block-coroutine-wrapper.html , it looks OK:

    A lot of functions in QEMU block layer (see <code class="docutils literal notranslate"><span class="pre">block/*</span></code>) can only be