linux-kernel - Re: [PATCH] kobject: return -ENOSPC when add_uevent

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Date:   Fri, 7 Jun 2019 20:53:28 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kobject: return -ENOSPC when add_uevent_var() fails

On Wed, Jun 5, 2019 at 5:53 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Tue, Jun 4, 2019 at 8:00 PM Masahiro Yamada
> <yamada.masahiro@...ionext.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@...ionext.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