sysfs, kernfs: introduce kernfs_notify()

Introduce kernfs interface to wake up poll(2) which takes and returns
sysfs_dirents.

sysfs_notify_dirent() is renamed to kernfs_notify() and sysfs_notify()
is updated so that it doesn't directly grab sysfs_mutex but acquires
the target sysfs_dirents using sysfs_get_dirent().
sysfs_notify_dirent() is reimplemented as a dumb inline wrapper around
kernfs_notify().

This patch doesn't introduce any behavior changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 22 insertions, 11 deletions

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 74e3478d9cb4..a68cbef3a674 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -851,7 +851,13 @@ static unsigned int kernfs_file_poll(struct file *filp, poll_table *wait)
         return DEFAULT_POLLMASK|POLLERR|POLLPRI;
 }
 
-void sysfs_notify_dirent(struct sysfs_dirent *sd)
+/**
+ * kernfs_notify - notify a kernfs file
+ * @sd: file to notify
+ *
+ * Notify @sd such that poll(2) on @sd wakes up.
+ */
+void kernfs_notify(struct sysfs_dirent *sd)
 {
         struct sysfs_open_dirent *od;
         unsigned long flags;
@@ -868,22 +874,27 @@ void sysfs_notify_dirent(struct sysfs_dirent *sd)
 
         spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags);
 }
-EXPORT_SYMBOL_GPL(sysfs_notify_dirent);
+EXPORT_SYMBOL_GPL(kernfs_notify);
 
 void sysfs_notify(struct kobject *k, const char *dir, const char *attr)
 {
-        struct sysfs_dirent *sd = k->sd;
-
-        mutex_lock(&sysfs_mutex);
+        struct sysfs_dirent *sd = k->sd, *tmp;
 
         if (sd && dir)
-                sd = sysfs_find_dirent(sd, dir, NULL);
-        if (sd && attr)
-                sd = sysfs_find_dirent(sd, attr, NULL);
-        if (sd)
-                sysfs_notify_dirent(sd);
+                sd = sysfs_get_dirent(sd, dir);
+        else
+                sysfs_get(sd);
 
-        mutex_unlock(&sysfs_mutex);
+        if (sd && attr) {
+                tmp = sysfs_get_dirent(sd, attr);
+                sysfs_put(sd);
+                sd = tmp;
+        }
+
+        if (sd) {
+                kernfs_notify(sd);
+                sysfs_put(sd);
+        }
 }
 EXPORT_SYMBOL_GPL(sysfs_notify);