[PATCH] kobject: return -ENOSPC when add_uevent_var() fails

[PATCH] kobject: return -ENOSPC when add_uevent_var() fails

[Masahiro Yamada]

This function never attempts to allocate memory, so returning -ENOMEM
looks weird to me. The reason of the failure is there is no more space
in the given kobj_uevent_env structure.

No caller of this function relies on this functing returning a specific
error code, so just change it to return -ENOSPC. The intended change,
if any, is the error number displayed in log messages.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 lib/kobject_uevent.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 7998affa45d4..5ffd44bf4aad 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -647,7 +647,7 @@ EXPORT_SYMBOL_GPL(kobject_uevent);
  * @env: environment buffer structure
  * @format: printf format for the key=value pair
  *
- * Returns 0 if environment variable was added successfully or -ENOMEM
+ * Returns 0 if environment variable was added successfully or -ENOSPC
  * if no space was available.
  */
 int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
@@ -657,7 +657,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
 
 	if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
 		WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
-		return -ENOMEM;
+		return -ENOSPC;
 	}
 
 	va_start(args, format);
@@ -668,7 +668,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
 
 	if (len >= (sizeof(env->buf) - env->buflen)) {
 		WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
-		return -ENOMEM;
+		return -ENOSPC;
 	}
 
 	env->envp[env->envp_idx++] = &env->buf[env->buflen];
-- 
2.17.1

Re: [PATCH] kobject: return -ENOSPC when add_uevent_var() fails

[Rafael J. Wysocki]

On Tue, Jun 4, 2019 at 8:00 PM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> This function never attempts to allocate memory, so returning -ENOMEM
> looks weird to me.

And why is the "looks weird to me" a good enough reason for making
changes like this?

The existing behavior is known and documented AFAICS and is it really
so confusing?

> The reason of the failure is there is no more space
> in the given kobj_uevent_env structure.
>
> No caller of this function relies on this functing returning a specific
> error code, so just change it to return -ENOSPC. The intended change,
> if any, is the error number displayed in log messages.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
>
>  lib/kobject_uevent.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> index 7998affa45d4..5ffd44bf4aad 100644
> --- a/lib/kobject_uevent.c
> +++ b/lib/kobject_uevent.c
> @@ -647,7 +647,7 @@ EXPORT_SYMBOL_GPL(kobject_uevent);
>   * @env: environment buffer structure
>   * @format: printf format for the key=value pair
>   *
> - * Returns 0 if environment variable was added successfully or -ENOMEM
> + * Returns 0 if environment variable was added successfully or -ENOSPC
>   * if no space was available.
>   */
>  int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
> @@ -657,7 +657,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
>
>         if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
>                 WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
> -               return -ENOMEM;
> +               return -ENOSPC;
>         }
>
>         va_start(args, format);
> @@ -668,7 +668,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
>
>         if (len >= (sizeof(env->buf) - env->buflen)) {
>                 WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
> -               return -ENOMEM;
> +               return -ENOSPC;
>         }
>
>         env->envp[env->envp_idx++] = &env->buf[env->buflen];
> --
> 2.17.1
>

Re: [PATCH] kobject: return -ENOSPC when add_uevent_var() fails

[Masahiro Yamada]

On Wed, Jun 5, 2019 at 5:53 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Tue, Jun 4, 2019 at 8:00 PM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
> >
> > This function never attempts to allocate memory, so returning -ENOMEM
> > looks weird to me.
>
> And why is the "looks weird to me" a good enough reason for making
> changes like this?


Since the code is read much more than written,
this change eliminates the question of "why -ENOMEM here?"



Masahiro Yamada


> The existing behavior is known and documented AFAICS and is it really
> so confusing?
>
> > The reason of the failure is there is no more space
> > in the given kobj_uevent_env structure.
> >
> > No caller of this function relies on this functing returning a specific
> > error code, so just change it to return -ENOSPC. The intended change,
> > if any, is the error number displayed in log messages.
> >
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > ---
> >
> >  lib/kobject_uevent.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> > index 7998affa45d4..5ffd44bf4aad 100644
> > --- a/lib/kobject_uevent.c
> > +++ b/lib/kobject_uevent.c
> > @@ -647,7 +647,7 @@ EXPORT_SYMBOL_GPL(kobject_uevent);
> >   * @env: environment buffer structure
> >   * @format: printf format for the key=value pair
> >   *
> > - * Returns 0 if environment variable was added successfully or -ENOMEM
> > + * Returns 0 if environment variable was added successfully or -ENOSPC
> >   * if no space was available.
> >   */
> >  int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
> > @@ -657,7 +657,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
> >
> >         if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
> >                 WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
> > -               return -ENOMEM;
> > +               return -ENOSPC;
> >         }
> >
> >         va_start(args, format);
> > @@ -668,7 +668,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
> >
> >         if (len >= (sizeof(env->buf) - env->buflen)) {
> >                 WARN(1, KERN_ERR "add_uevent_var: buffer size too small\n");
> > -               return -ENOMEM;
> > +               return -ENOSPC;
> >         }
> >
> >         env->envp[env->envp_idx++] = &env->buf[env->buflen];
> > --
> > 2.17.1

Re: [PATCH] kobject: return -ENOSPC when add_uevent_var() fails

[Rafael J. Wysocki]

On Fri, Jun 7, 2019 at 2:02 PM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> On Wed, Jun 5, 2019 at 5:53 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
> >
> > On Tue, Jun 4, 2019 at 8:00 PM Masahiro Yamada
> > <yamada.masahiro@socionext.com> wrote:
> > >
> > > This function never attempts to allocate memory, so returning -ENOMEM
> > > looks weird to me.
> >
> > And why is the "looks weird to me" a good enough reason for making
> > changes like this?
>
>
> Since the code is read much more than written,
> this change eliminates the question of "why -ENOMEM here?"

And you are sure that nobody relies on the current return value?

Re: [PATCH] kobject: return -ENOSPC when add_uevent_var() fails

[Greg Kroah-Hartman]

On Wed, Jun 05, 2019 at 02:44:12AM +0900, Masahiro Yamada wrote:
> This function never attempts to allocate memory, so returning -ENOMEM
> looks weird to me. The reason of the failure is there is no more space
> in the given kobj_uevent_env structure.
> 
> No caller of this function relies on this functing returning a specific
> error code, so just change it to return -ENOSPC. The intended change,
> if any, is the error number displayed in log messages.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
> 
>  lib/kobject_uevent.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> index 7998affa45d4..5ffd44bf4aad 100644
> --- a/lib/kobject_uevent.c
> +++ b/lib/kobject_uevent.c
> @@ -647,7 +647,7 @@ EXPORT_SYMBOL_GPL(kobject_uevent);
>   * @env: environment buffer structure
>   * @format: printf format for the key=value pair
>   *
> - * Returns 0 if environment variable was added successfully or -ENOMEM
> + * Returns 0 if environment variable was added successfully or -ENOSPC
>   * if no space was available.
>   */
>  int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
> @@ -657,7 +657,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
>  
>  	if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
>  		WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
> -		return -ENOMEM;
> +		return -ENOSPC;

As Rafael says, changing this for no good reason is not a good idea,
sorry.  Let's live with it as-is unless you can show some place where
this specific error value is causing problems.

thanks,

greg k-h

Re: [PATCH] kobject: return -ENOSPC when add_uevent_var() fails

[Masahiro Yamada]

On Tue, Jun 11, 2019 at 2:47 AM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Wed, Jun 05, 2019 at 02:44:12AM +0900, Masahiro Yamada wrote:
> > This function never attempts to allocate memory, so returning -ENOMEM
> > looks weird to me. The reason of the failure is there is no more space
> > in the given kobj_uevent_env structure.
> >
> > No caller of this function relies on this functing returning a specific
> > error code, so just change it to return -ENOSPC. The intended change,
> > if any, is the error number displayed in log messages.
> >
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > ---
> >
> >  lib/kobject_uevent.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> > index 7998affa45d4..5ffd44bf4aad 100644
> > --- a/lib/kobject_uevent.c
> > +++ b/lib/kobject_uevent.c
> > @@ -647,7 +647,7 @@ EXPORT_SYMBOL_GPL(kobject_uevent);
> >   * @env: environment buffer structure
> >   * @format: printf format for the key=value pair
> >   *
> > - * Returns 0 if environment variable was added successfully or -ENOMEM
> > + * Returns 0 if environment variable was added successfully or -ENOSPC
> >   * if no space was available.
> >   */
> >  int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
> > @@ -657,7 +657,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
> >
> >       if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
> >               WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
> > -             return -ENOMEM;
> > +             return -ENOSPC;
>
> As Rafael says, changing this for no good reason is not a good idea,
> sorry.  Let's live with it as-is unless you can show some place where
> this specific error value is causing problems.



Didn't you see WARN() above the return code?
I rephrased the commit log for clarification in v2.

Thanks.


-- 
Best Regards
Masahiro Yamada

Re: [PATCH] kobject: return -ENOSPC when add_uevent_var() fails

[Greg Kroah-Hartman]

On Tue, Jun 11, 2019 at 06:09:55AM +0900, Masahiro Yamada wrote:
> On Tue, Jun 11, 2019 at 2:47 AM Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Wed, Jun 05, 2019 at 02:44:12AM +0900, Masahiro Yamada wrote:
> > > This function never attempts to allocate memory, so returning -ENOMEM
> > > looks weird to me. The reason of the failure is there is no more space
> > > in the given kobj_uevent_env structure.
> > >
> > > No caller of this function relies on this functing returning a specific
> > > error code, so just change it to return -ENOSPC. The intended change,
> > > if any, is the error number displayed in log messages.
> > >
> > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > > ---
> > >
> > >  lib/kobject_uevent.c | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> > > index 7998affa45d4..5ffd44bf4aad 100644
> > > --- a/lib/kobject_uevent.c
> > > +++ b/lib/kobject_uevent.c
> > > @@ -647,7 +647,7 @@ EXPORT_SYMBOL_GPL(kobject_uevent);
> > >   * @env: environment buffer structure
> > >   * @format: printf format for the key=value pair
> > >   *
> > > - * Returns 0 if environment variable was added successfully or -ENOMEM
> > > + * Returns 0 if environment variable was added successfully or -ENOSPC
> > >   * if no space was available.
> > >   */
> > >  int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
> > > @@ -657,7 +657,7 @@ int add_uevent_var(struct kobj_uevent_env *env, const char *format, ...)
> > >
> > >       if (env->envp_idx >= ARRAY_SIZE(env->envp)) {
> > >               WARN(1, KERN_ERR "add_uevent_var: too many keys\n");
> > > -             return -ENOMEM;
> > > +             return -ENOSPC;
> >
> > As Rafael says, changing this for no good reason is not a good idea,
> > sorry.  Let's live with it as-is unless you can show some place where
> > this specific error value is causing problems.
> 
> 
> 
> Didn't you see WARN() above the return code?

Yes.

> I rephrased the commit log for clarification in v2.

It still doesn't matter :)

thanks,

greg k-h