The new helper function is to check whether the class file is existing
or not. This function will be used by networking stack to
check "/sys/class/net/*" file.
Reported-by: [email protected]
Fixes: b76cdba9cdb2 ("[PATCH] bonding: add sysfs functionality to bonding (large)")
Signed-off-by: Taehee Yoo <[email protected]>
---
v1 -> v2:
- Implement class_has_file_ns() instead of class_find_and_get_file_ns().
- Change headline.
- Add kernel documentation comment.
drivers/base/class.c | 22 ++++++++++++++++++++++
include/linux/device/class.h | 3 ++-
2 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/drivers/base/class.c b/drivers/base/class.c
index bcd410e6d70a..a2f2787f6aa7 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -105,6 +105,28 @@ void class_remove_file_ns(struct class *cls, const struct class_attribute *attr,
sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
}
+/**
+ * class_has_file_ns - check whether file is existing or not
+ * @cls: the compatibility class
+ * @name: name to look for
+ * @ns: the namespace tag to use
+ */
+bool class_has_file_ns(struct class *cls, const char *name,
+ const void *ns)
+{
+ struct kernfs_node *kn = NULL;
+
+ if (cls) {
+ kn = kernfs_find_and_get_ns(cls->p->subsys.kobj.sd, name, ns);
+ if (kn) {
+ kernfs_put(kn);
+ return true;
+ }
+ }
+ return false;
+}
+EXPORT_SYMBOL_GPL(class_has_file_ns);
+
static struct class *class_get(struct class *cls)
{
if (cls)
diff --git a/include/linux/device/class.h b/include/linux/device/class.h
index e8d470c457d1..b3d43658b201 100644
--- a/include/linux/device/class.h
+++ b/include/linux/device/class.h
@@ -209,7 +209,8 @@ extern int __must_check class_create_file_ns(struct class *class,
extern void class_remove_file_ns(struct class *class,
const struct class_attribute *attr,
const void *ns);
-
+bool class_has_file_ns(struct class *cls, const char *name,
+ const void *ns);
static inline int __must_check class_create_file(struct class *class,
const struct class_attribute *attr)
{
--
2.17.1
On Sat, Apr 04, 2020 at 02:18:27PM +0000, Taehee Yoo wrote:
> The new helper function is to check whether the class file is existing
> or not. This function will be used by networking stack to
> check "/sys/class/net/*" file.
>
> Reported-by: [email protected]
> Fixes: b76cdba9cdb2 ("[PATCH] bonding: add sysfs functionality to bonding (large)")
> Signed-off-by: Taehee Yoo <[email protected]>
> ---
>
> v1 -> v2:
> - Implement class_has_file_ns() instead of class_find_and_get_file_ns().
> - Change headline.
> - Add kernel documentation comment.
>
> drivers/base/class.c | 22 ++++++++++++++++++++++
> include/linux/device/class.h | 3 ++-
> 2 files changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/class.c b/drivers/base/class.c
> index bcd410e6d70a..a2f2787f6aa7 100644
> --- a/drivers/base/class.c
> +++ b/drivers/base/class.c
> @@ -105,6 +105,28 @@ void class_remove_file_ns(struct class *cls, const struct class_attribute *attr,
> sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
> }
>
> +/**
> + * class_has_file_ns - check whether file is existing or not
> + * @cls: the compatibility class
> + * @name: name to look for
> + * @ns: the namespace tag to use
> + */
> +bool class_has_file_ns(struct class *cls, const char *name,
> + const void *ns)
Why would you use this? And what happens if the file shows up, or goes
away, instantly after this call is made?
This feels very broken.
greg k-h
On Sun, 5 Apr 2020 at 00:50, Greg KH <[email protected]> wrote:
>
Hi Greg,
Thank you for your review!
> On Sat, Apr 04, 2020 at 02:18:27PM +0000, Taehee Yoo wrote:
> > The new helper function is to check whether the class file is existing
> > or not. This function will be used by networking stack to
> > check "/sys/class/net/*" file.
> >
> > Reported-by: [email protected]
> > Fixes: b76cdba9cdb2 ("[PATCH] bonding: add sysfs functionality to bonding (large)")
> > Signed-off-by: Taehee Yoo <[email protected]>
> > ---
> >
> > v1 -> v2:
> > - Implement class_has_file_ns() instead of class_find_and_get_file_ns().
> > - Change headline.
> > - Add kernel documentation comment.
> >
> > drivers/base/class.c | 22 ++++++++++++++++++++++
> > include/linux/device/class.h | 3 ++-
> > 2 files changed, 24 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/class.c b/drivers/base/class.c
> > index bcd410e6d70a..a2f2787f6aa7 100644
> > --- a/drivers/base/class.c
> > +++ b/drivers/base/class.c
> > @@ -105,6 +105,28 @@ void class_remove_file_ns(struct class *cls, const struct class_attribute *attr,
> > sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
> > }
> >
> > +/**
> > + * class_has_file_ns - check whether file is existing or not
> > + * @cls: the compatibility class
> > + * @name: name to look for
> > + * @ns: the namespace tag to use
> > + */
> > +bool class_has_file_ns(struct class *cls, const char *name,
> > + const void *ns)
>
> Why would you use this? And what happens if the file shows up, or goes
> away, instantly after this call is made?
>
> This feels very broken.
>
Ah, I missed considering other usescases.
If other users don't use locks, this function would return incorrect
information. The problem seems to become from that this function
calls kernfs_put().
Thanks a lot!
Taehee Yoo