Commit d911d987 authored Apr 09, 2014 by Tejun Heo Committed by Greg Kroah-Hartman Apr 25, 2014

kernfs: make kernfs_notify() trigger inotify events too



kernfs_notify() is used to indicate either new data is available or
the content of a file has changed.  It currently only triggers poll
which may not be the most convenient to monitor especially when there
are a lot to monitor.  Let's hook it up to fsnotify too so that the
events can be monitored via inotify too.

fsnotify_modify() requires file * but kernfs_notify() doesn't have any
specific file associated; however, we can walk all super_blocks
associated with a kernfs_root and as kernfs always associate one ino
with inode and one dentry with an inode, it's trivial to look up the
dentry associated with a given kernfs_node.  As any active monitor
would pin dentry, just looking up existing dentry is enough.  This
patch looks up the dentry associated with the specified kernfs_node
and generates events equivalent to fsnotify_modify().

Note that as fsnotify doesn't provide fsnotify_modify() equivalent
which can be called with dentry, kernfs_notify() directly calls
fsnotify_parent() and fsnotify().  It might be better to add a wrapper
in fsnotify.h instead.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: John McCutchan <john@johnmccutchan.com>
Cc: Robert Love <rlove@rlove.org>
Cc: Eric Paris <eparis@parisplace.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 7d568a83

fs/kernfs/file.c

+35 −6

Original line number	Diff line number	Diff line
		@@ -14,6 +14,7 @@
		#include <linux/poll.h>
		#include <linux/pagemap.h>
		#include <linux/sched.h>
		#include <linux/fsnotify.h>

		#include "kernfs-internal.h"

		@@ -785,20 +786,48 @@ static unsigned int kernfs_fop_poll(struct file filp, poll_table wait)
		*/
		void kernfs_notify(struct kernfs_node *kn)
		{
		struct kernfs_root *root = kernfs_root(kn);
		struct kernfs_open_node *on;
		struct kernfs_super_info *info;
		unsigned long flags;

		if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
		return;

		/* kick poll */
		spin_lock_irqsave(&kernfs_open_node_lock, flags);

		if (!WARN_ON(kernfs_type(kn) != KERNFS_FILE)) {
		on = kn->attr.open;
		if (on) {
		atomic_inc(&on->event);
		wake_up_interruptible(&on->poll);
		}
		}

		spin_unlock_irqrestore(&kernfs_open_node_lock, flags);

		/* kick fsnotify */
		mutex_lock(&kernfs_mutex);

		list_for_each_entry(info, &root->supers, node) {
		struct inode *inode;
		struct dentry *dentry;

		inode = ilookup(info->sb, kn->ino);
		if (!inode)
		continue;

		dentry = d_find_any_alias(inode);
		if (dentry) {
		fsnotify_parent(NULL, dentry, FS_MODIFY);
		fsnotify(inode, FS_MODIFY, inode, FSNOTIFY_EVENT_INODE,
		NULL, 0);
		dput(dentry);
		}

		iput(inode);
		}

		mutex_unlock(&kernfs_mutex);
		}
		EXPORT_SYMBOL_GPL(kernfs_notify);