2010-12-12 12:42:59

by Rodolfo Giometti

Subject: fsnotify & sysfs

Hello,

I know that a sysfs file may be pollable but I'm asking to myself how
it could be difficult adding notifying support also.

Maybe adding a call to the fsnotify subsystem within the
sysfs_notify() function as follow can do the trick?

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index da3fefe..afee69f 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -484,8 +486,10 @@ void sysfs_notify(struct kobject *k, const char
*dir, const
sd = sysfs_find_dirent(sd, NULL, dir);
if (sd && attr)
sd = sysfs_find_dirent(sd, NULL, attr);
- if (sd)
+ if (sd) {
sysfs_notify_dirent(sd);
+ fsnotify_change(dentry, ATTR_SIZE);
+ }

mutex_unlock(&sysfs_mutex);
}

However my problem is how to get the struct dentry pointer needed by
fsnotify_change() related to the struct sysfs_dirent pointer passed to
sysfs_notify(). :(

Can you please give me any advice about to solve it?

Another question: in file linux/fs/sysfs/file.c I see:

#include <linux/fsnotify.h>

but none of its functions are called into file.c... maybe it's a
mistake?

Thanks in advance,

Rodolfo

--

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2010-12-12 16:46:32

by Greg KH

Subject: Re: fsnotify & sysfs

On Sun, Dec 12, 2010 at 01:42:47PM +0100, Rodolfo Giometti wrote:
> Hello,
>
> I know that a sysfs file may be pollable but I'm asking to myself how
> it could be difficult adding notifying support also.
>
> Maybe adding a call to the fsnotify subsystem within the
> sysfs_notify() function as follow can do the trick?

Perhaps, does that work?

> However my problem is how to get the struct dentry pointer needed by
> fsnotify_change() related to the struct sysfs_dirent pointer passed to
> sysfs_notify(). :(

Yup, that's a problem :(

> Can you please give me any advice about to solve it?
>
> Another question: in file linux/fs/sysfs/file.c I see:
>
> #include <linux/fsnotify.h>
>
> but none of its functions are called into file.c... maybe it's a
> mistake?

Possibly, but look at the patch that added that line, perhaps it was put
there for a reason.

thanks,

greg k-h