[PATCH v2 1/3] kernfs: allow passing fsnotify event types

["T.J. Mercier" <tjmercier@google.com>]

The kernfs_notify function is hardcoded to only issue FS_MODIFY events
since that is the only current use case. Allow for supporting other
events by adding a notify_event field to kernfs_elem_attr. The
limitation of only one queued event per kernfs_node continues to exist
as a consequence of the design of the kernfs_notify_list. The new
notify_event field is protected by the same kernfs_notify_lock as the
existing notify_next field.

Signed-off-by: T.J. Mercier <tjmercier@google.com>
---
 fs/kernfs/file.c       | 8 ++++++--
 include/linux/kernfs.h | 1 +
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
index 9adf36e6364b..e978284ff983 100644
--- a/fs/kernfs/file.c
+++ b/fs/kernfs/file.c
@@ -914,6 +914,7 @@ static void kernfs_notify_workfn(struct work_struct *work)
 	struct kernfs_node *kn;
 	struct kernfs_super_info *info;
 	struct kernfs_root *root;
+	u32 notify_event;
 repeat:
 	/* pop one off the notify_list */
 	spin_lock_irq(&kernfs_notify_lock);
@@ -924,6 +925,8 @@ static void kernfs_notify_workfn(struct work_struct *work)
 	}
 	kernfs_notify_list = kn->attr.notify_next;
 	kn->attr.notify_next = NULL;
+	notify_event = kn->attr.notify_event;
+	kn->attr.notify_event = 0;
 	spin_unlock_irq(&kernfs_notify_lock);
 
 	root = kernfs_root(kn);
@@ -954,7 +957,7 @@ static void kernfs_notify_workfn(struct work_struct *work)
 		if (parent) {
 			p_inode = ilookup(info->sb, kernfs_ino(parent));
 			if (p_inode) {
-				fsnotify(FS_MODIFY | FS_EVENT_ON_CHILD,
+				fsnotify(notify_event | FS_EVENT_ON_CHILD,
 					 inode, FSNOTIFY_EVENT_INODE,
 					 p_inode, &name, inode, 0);
 				iput(p_inode);
@@ -964,7 +967,7 @@ static void kernfs_notify_workfn(struct work_struct *work)
 		}
 
 		if (!p_inode)
-			fsnotify_inode(inode, FS_MODIFY);
+			fsnotify_inode(inode, notify_event);
 
 		iput(inode);
 	}
@@ -1005,6 +1008,7 @@ void kernfs_notify(struct kernfs_node *kn)
 	if (!kn->attr.notify_next) {
 		kernfs_get(kn);
 		kn->attr.notify_next = kernfs_notify_list;
+		kn->attr.notify_event = FS_MODIFY;
 		kernfs_notify_list = kn;
 		schedule_work(&kernfs_notify_work);
 	}
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index b5a5f32fdfd1..1762b32c1a8e 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -181,6 +181,7 @@ struct kernfs_elem_attr {
 	struct kernfs_open_node __rcu	*open;
 	loff_t			size;
 	struct kernfs_node	*notify_next;	/* for kernfs_notify() */
+	u32			notify_event;   /* for kernfs_notify() */
 };
 
 /*
-- 
2.53.0.273.g2a3d683680-goog