[PATCH v6 4/7] scripts: add coroutine-wrapper.py

[Vladimir Sementsov-Ogievskiy]

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, use separate bool for void functions
  - 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/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>
---
 Makefile                             |   8 ++
 block/block-gen.h                    |  55 +++++++++
 include/block/generated-co-wrapper.h |  35 ++++++
 block/Makefile.objs                  |   1 +
 scripts/coroutine-wrapper.py         | 174 +++++++++++++++++++++++++++
 5 files changed, 273 insertions(+)
 create mode 100644 block/block-gen.h
 create mode 100644 include/block/generated-co-wrapper.h
 create mode 100755 scripts/coroutine-wrapper.py

diff --git a/Makefile b/Makefile
index d1af126ea1..517a29810f 100644
--- a/Makefile
+++ b/Makefile
@@ -175,6 +175,14 @@ generated-files-y += $(TRACE_SOURCES)
 generated-files-y += $(BUILD_DIR)/trace-events-all
 generated-files-y += .git-submodule-status
 
+generated-files-y += block/block-gen.c
+
+COROUTINE_HEADERS = include/block/block.h block/coroutines.h
+block/block-gen.c: $(COROUTINE_HEADERS) scripts/coroutine-wrapper.py
+       $(call quiet-command, \
+               cat $(addprefix $(SRC_PATH)/,$(COROUTINE_HEADERS)) | \
+               $(SRC_PATH)/scripts/coroutine-wrapper.py > 
$@,"GEN","$(TARGET_DIR)$@")
+
 trace-group-name = $(shell dirname $1 | sed -e 's/[^a-zA-Z0-9]/_/g')
 
 tracetool-y = $(SRC_PATH)/scripts/tracetool.py
diff --git a/block/block-gen.h b/block/block-gen.h
new file mode 100644
index 0000000000..482d06737d
--- /dev/null
+++ b/block/block-gen.h
@@ -0,0 +1,55 @@
+/*
+ * 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.
+ */
+
+#ifndef BLOCK_BLOCK_GEN_H
+#define BLOCK_BLOCK_GEN_H
+
+#include "block/block_int.h"
+
+/* This function is called at the end of generated coroutine entries. */
+static inline void bdrv_poll_co__on_exit(void)
+{
+    aio_wait_kick();
+}
+
+/* Base structure for argument packing structures */
+typedef struct BdrvPollCo {
+    BlockDriverState *bs;
+    bool in_progress;
+    int ret;
+    Coroutine *co; /* Keep pointer here for debugging */
+} BdrvPollCo;
+
+static inline int bdrv_poll_co(BdrvPollCo *s)
+{
+    assert(!qemu_in_coroutine());
+
+    bdrv_coroutine_enter(s->bs, s->co);
+    BDRV_POLL_WHILE(s->bs, s->in_progress);
+
+    return s->ret;
+}
+
+#endif /* BLOCK_BLOCK_GEN_H */
diff --git a/include/block/generated-co-wrapper.h 
b/include/block/generated-co-wrapper.h
new file mode 100644
index 0000000000..62c6e053ba
--- /dev/null
+++ b/include/block/generated-co-wrapper.h
@@ -0,0 +1,35 @@
+/*
+ * Block layer I/O functions
+ *
+ * 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.
+ */
+
+#ifndef BLOCK_GENERATED_CO_WRAPPER_H
+#define BLOCK_GENERATED_CO_WRAPPER_H
+
+/*
+ * generated_co_wrapper
+ * Function specifier, which does nothing but marking functions to be
+ * generated by scripts/coroutine-wrapper.py
+ */
+#define generated_co_wrapper
+
+#endif /* BLOCK_GENERATED_CO_WRAPPER_H */
diff --git a/block/Makefile.objs b/block/Makefile.objs
index 3635b6b4c1..05e4d033c1 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -45,6 +45,7 @@ block-obj-y += crypto.o
 block-obj-y += aio_task.o
 block-obj-y += backup-top.o
 block-obj-y += filter-compress.o
+block-obj-y += block-gen.o
 common-obj-y += monitor/
 
 block-obj-y += stream.o
diff --git a/scripts/coroutine-wrapper.py b/scripts/coroutine-wrapper.py
new file mode 100755
index 0000000000..dbe6fb97d9
--- /dev/null
+++ b/scripts/coroutine-wrapper.py
@@ -0,0 +1,174 @@
+#!/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
+and generates corresponding wrappers on stdout.
+
+Usage: cat FILE.[ch]... | coroutine-wrapper.py > generated-file.c
+
+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/>.
+"""
+
+import sys
+import re
+import subprocess
+from typing import Iterator
+
+
+def prettify(code: str) -> str:
+    """Prettify code using clang-format if available"""
+
+    try:
+        style = '{IndentWidth: 4, BraceWrapping: {AfterFunction: true}, ' \
+            'BreakBeforeBraces: Custom, SortIncludes: false, ' \
+            'MaxEmptyLinesToKeep: 2}'
+        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/coroutine-wrapper.py
+ *
+{copyright}
+ */
+
+#include "qemu/osdep.h"
+#include "block/coroutines.h"
+#include "block/block-gen.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}') });
+    s->poll_state.in_progress = false;
+
+    bdrv_poll_co__on_exit();
+}}
+
+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__':
+    print(gen_wrappers_file(sys.stdin.read()))
-- 
2.21.0