From: Jiri Pirko <[email protected]>
With introduction of __free() macro using cleanup infrastructure, it
will very likely become quite common to see following pattern:
type *var __free(kfree) = kzalloc(sizeof(*var), GFP_KERNEL);
To follow the CLASS() flow from cleanup.h, introduce a simple macro
KZALLOC_FREE() to wrap this over and allow the same flow.
Show an example usage in gpio-sim driver.
Signed-off-by: Jiri Pirko <[email protected]>
---
drivers/gpio/gpio-sim.c | 3 +--
include/linux/slab.h | 3 +++
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/gpio/gpio-sim.c b/drivers/gpio/gpio-sim.c
index c4106e37e6db..997237b3d80c 100644
--- a/drivers/gpio/gpio-sim.c
+++ b/drivers/gpio/gpio-sim.c
@@ -1496,8 +1496,7 @@ gpio_sim_config_make_device_group(struct config_group *group, const char *name)
{
int id;
- struct gpio_sim_device *dev __free(kfree) = kzalloc(sizeof(*dev),
- GFP_KERNEL);
+ KZALLOC_FREE(struct gpio_sim_device *, dev, GFP_KERNEL);
if (!dev)
return ERR_PTR(-ENOMEM);
diff --git a/include/linux/slab.h b/include/linux/slab.h
index b5f5ee8308d0..baee6acd58d3 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -711,6 +711,9 @@ static inline __alloc_size(1) void *kzalloc(size_t size, gfp_t flags)
return kmalloc(size, flags | __GFP_ZERO);
}
+#define KZALLOC_FREE(_type, var, _gfp_t) \
+ _type var __free(kfree) = kzalloc(sizeof(*var), _gfp_t)
+
/**
* kzalloc_node - allocate zeroed memory from a particular memory node.
* @size: how many bytes of memory are required.
--
2.44.0
On Fri, 15 Mar 2024, Jiri Pirko wrote:
> From: Jiri Pirko <[email protected]>
>
> With introduction of __free() macro using cleanup infrastructure, it
> will very likely become quite common to see following pattern:
> type *var __free(kfree) = kzalloc(sizeof(*var), GFP_KERNEL);
>
> To follow the CLASS() flow from cleanup.h, introduce a simple macro
> KZALLOC_FREE() to wrap this over and allow the same flow.
>
> Show an example usage in gpio-sim driver.
>
Seems highly specialized especially for kzalloc specifically, so not sure
this warrants its own macro.
> Signed-off-by: Jiri Pirko <[email protected]>
> ---
> drivers/gpio/gpio-sim.c | 3 +--
> include/linux/slab.h | 3 +++
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpio-sim.c b/drivers/gpio/gpio-sim.c
> index c4106e37e6db..997237b3d80c 100644
> --- a/drivers/gpio/gpio-sim.c
> +++ b/drivers/gpio/gpio-sim.c
> @@ -1496,8 +1496,7 @@ gpio_sim_config_make_device_group(struct config_group *group, const char *name)
> {
> int id;
>
> - struct gpio_sim_device *dev __free(kfree) = kzalloc(sizeof(*dev),
> - GFP_KERNEL);
> + KZALLOC_FREE(struct gpio_sim_device *, dev, GFP_KERNEL);
> if (!dev)
> return ERR_PTR(-ENOMEM);
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index b5f5ee8308d0..baee6acd58d3 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -711,6 +711,9 @@ static inline __alloc_size(1) void *kzalloc(size_t size, gfp_t flags)
> return kmalloc(size, flags | __GFP_ZERO);
> }
>
> +#define KZALLOC_FREE(_type, var, _gfp_t) \
> + _type var __free(kfree) = kzalloc(sizeof(*var), _gfp_t)
> +
> /**
> * kzalloc_node - allocate zeroed memory from a particular memory node.
> * @size: how many bytes of memory are required.
> --
> 2.44.0
>
>
Fri, Mar 15, 2024 at 10:39:02PM CET, [email protected] wrote:
>On Fri, 15 Mar 2024, Jiri Pirko wrote:
>
>> From: Jiri Pirko <[email protected]>
>>
>> With introduction of __free() macro using cleanup infrastructure, it
>> will very likely become quite common to see following pattern:
>> type *var __free(kfree) = kzalloc(sizeof(*var), GFP_KERNEL);
>>
>> To follow the CLASS() flow from cleanup.h, introduce a simple macro
>> KZALLOC_FREE() to wrap this over and allow the same flow.
>>
>> Show an example usage in gpio-sim driver.
>>
>
>Seems highly specialized especially for kzalloc specifically, so not sure
>this warrants its own macro.
Yeah, but having like 2-3 macro variants would probably cover vast
majority of usecases now. The rest could still do things manually.
> From: Jiri Pirko <[email protected]>
>
> With introduction of __free() macro using cleanup infrastructure, it
> will very likely become quite common to see following pattern:
> type *var __free(kfree) = kzalloc(sizeof(*var), GFP_KERNEL);
>
> To follow the CLASS() flow from cleanup.h, introduce a simple macro
> KZALLOC_FREE() to wrap this over and allow the same flow.
>
> Show an example usage in gpio-sim driver.
>
> Signed-off-by: Jiri Pirko <[email protected]>
> ---
> drivers/gpio/gpio-sim.c | 3 +--
> include/linux/slab.h | 3 +++
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpio/gpio-sim.c b/drivers/gpio/gpio-sim.c
> index c4106e37e6db..997237b3d80c 100644
> --- a/drivers/gpio/gpio-sim.c
> +++ b/drivers/gpio/gpio-sim.c
> @@ -1496,8 +1496,7 @@ gpio_sim_config_make_device_group(struct config_group *group, const char *name)
> {
> int id;
>
> - struct gpio_sim_device *dev __free(kfree) = kzalloc(sizeof(*dev),
> - GFP_KERNEL);
> + KZALLOC_FREE(struct gpio_sim_device *, dev, GFP_KERNEL);
> if (!dev)
> return ERR_PTR(-ENOMEM);
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index b5f5ee8308d0..baee6acd58d3 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -711,6 +711,9 @@ static inline __alloc_size(1) void *kzalloc(size_t size, gfp_t flags)
> return kmalloc(size, flags | __GFP_ZERO);
> }
>
> +#define KZALLOC_FREE(_type, var, _gfp_t) \
> + _type var __free(kfree) = kzalloc(sizeof(*var), _gfp_t)
> +
Nice, but I would rather see this wrapper in the cleanup.h file, that have all
of the rest of related stuff.
On top of that, I want to propose also a wrapper that is simpler in that it
does not allocate but just assigns null, with that in mind `_FREE` part of your
proposed name does not sound right.
Most of the similar functions that define or declare something are named
DEFINE_STH...
(Please CC me on any future version, I have to go, sorry).
> /**
> * kzalloc_node - allocate zeroed memory from a particular memory node.
> * @size: how many bytes of memory are required.
> --
> 2.44.0
>
>
Przemek Kitszel wrote:
> > From: Jiri Pirko <[email protected]>
> >
> > With introduction of __free() macro using cleanup infrastructure, it
> > will very likely become quite common to see following pattern:
> > type *var __free(kfree) = kzalloc(sizeof(*var), GFP_KERNEL);
> >
> > To follow the CLASS() flow from cleanup.h, introduce a simple macro
> > KZALLOC_FREE() to wrap this over and allow the same flow.
> >
> > Show an example usage in gpio-sim driver.
> >
> > Signed-off-by: Jiri Pirko <[email protected]>
> > ---
> > drivers/gpio/gpio-sim.c | 3 +--
> > include/linux/slab.h | 3 +++
> > 2 files changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpio/gpio-sim.c b/drivers/gpio/gpio-sim.c
> > index c4106e37e6db..997237b3d80c 100644
> > --- a/drivers/gpio/gpio-sim.c
> > +++ b/drivers/gpio/gpio-sim.c
> > @@ -1496,8 +1496,7 @@ gpio_sim_config_make_device_group(struct config_group *group, const char *name)
> > {
> > int id;
> >
> > - struct gpio_sim_device *dev __free(kfree) = kzalloc(sizeof(*dev),
> > - GFP_KERNEL);
> > + KZALLOC_FREE(struct gpio_sim_device *, dev, GFP_KERNEL);
> > if (!dev)
> > return ERR_PTR(-ENOMEM);
> >
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index b5f5ee8308d0..baee6acd58d3 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -711,6 +711,9 @@ static inline __alloc_size(1) void *kzalloc(size_t size, gfp_t flags)
> > return kmalloc(size, flags | __GFP_ZERO);
> > }
> >
> > +#define KZALLOC_FREE(_type, var, _gfp_t) \
> > + _type var __free(kfree) = kzalloc(sizeof(*var), _gfp_t)
> > +
>
> Nice, but I would rather see this wrapper in the cleanup.h file, that have all
> of the rest of related stuff.
>
> On top of that, I want to propose also a wrapper that is simpler in that it
> does not allocate but just assigns null, with that in mind `_FREE` part of your
> proposed name does not sound right.
No, do not hide assignments within macros
http://lore.kernel.org/r/CAHk-=whYxkfLVtBW_B-PgNqhKOAThTbfoH5CxtOTkwOB6VOt6w@mail.gmail.com
I.e. the amount of incremenal cleverness that include/linux/cleanup.h
will tolerate is low. Any helper should look like typical C.
On 3/25/24 20:00, Dan Williams wrote:
> Przemek Kitszel wrote:
>>> From: Jiri Pirko <[email protected]>
>>>
>>> With introduction of __free() macro using cleanup infrastructure, it
>>> will very likely become quite common to see following pattern:
>>> type *var __free(kfree) = kzalloc(sizeof(*var), GFP_KERNEL);
>>>
>>> To follow the CLASS() flow from cleanup.h, introduce a simple macro
>>> KZALLOC_FREE() to wrap this over and allow the same flow.
>>>
>>> Show an example usage in gpio-sim driver.
>>>
>>> Signed-off-by: Jiri Pirko <[email protected]>
>>> ---
>>> drivers/gpio/gpio-sim.c | 3 +--
>>> include/linux/slab.h | 3 +++
>>> 2 files changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpio/gpio-sim.c b/drivers/gpio/gpio-sim.c
>>> index c4106e37e6db..997237b3d80c 100644
>>> --- a/drivers/gpio/gpio-sim.c
>>> +++ b/drivers/gpio/gpio-sim.c
>>> @@ -1496,8 +1496,7 @@ gpio_sim_config_make_device_group(struct config_group *group, const char *name)
>>> {
>>> int id;
>>>
>>> - struct gpio_sim_device *dev __free(kfree) = kzalloc(sizeof(*dev),
>>> - GFP_KERNEL);
>>> + KZALLOC_FREE(struct gpio_sim_device *, dev, GFP_KERNEL);
>>> if (!dev)
>>> return ERR_PTR(-ENOMEM);
>>>
>>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>>> index b5f5ee8308d0..baee6acd58d3 100644
>>> --- a/include/linux/slab.h
>>> +++ b/include/linux/slab.h
>>> @@ -711,6 +711,9 @@ static inline __alloc_size(1) void *kzalloc(size_t size, gfp_t flags)
>>> return kmalloc(size, flags | __GFP_ZERO);
>>> }
>>>
>>> +#define KZALLOC_FREE(_type, var, _gfp_t) \
>>> + _type var __free(kfree) = kzalloc(sizeof(*var), _gfp_t)
>>> +
>>
>> Nice, but I would rather see this wrapper in the cleanup.h file, that have all
>> of the rest of related stuff.
>>
>> On top of that, I want to propose also a wrapper that is simpler in that it
>> does not allocate but just assigns null, with that in mind `_FREE` part of your
>> proposed name does not sound right.
>
> No, do not hide assignments within macros
As most general advice I agree, but here we have a specific case:
declare variable via macro; and that, (given the macro name would be
clearer), is expected to have assignment (or default (un)init).
I would even go one step further and remove also the asterisk from the
call site (and *hide* it in the macro definition).
See _DEFINE_FLEX() as example:
(there we change on-stack instead $this_thread on-heap-autofree)
https://elixir.bootlin.com/linux/v6.9-rc1/source/include/linux/overflow.h#L401
>
> http://lore.kernel.org/r/CAHk-=whYxkfLVtBW_B-PgNqhKOAThTbfoH5CxtOTkwOB6VOt6w@mail.gmail.com
Your thread is a more complex thing to what we have here.
And BTW, your original proposed solution is nice, and even if it hides
flow inside, it's almost obvious (the `return -EINTR` statement
is verbatim at call site). Allowing `else return -EINTR;` solution
proposed by @Linus is nicer, makes a good idiom, but is less obvious:
Imagine two developers that don't know the API (well), one writes:
`scoped_cond_guard(args);` and forgets to handle the error case,
the other by just looking at the code have no idea to append
`else handle_err();`.
>
> I.e. the amount of incremenal cleverness that include/linux/cleanup.h
> will tolerate is low. Any helper should look like typical C