3 files changed, 202 insertions, 0 deletions
diff --git a/fs/notify/dnotify/Kconfig b/fs/notify/dnotify/Kconfig
new file mode 100644
index 000000000000..26adf5dfa646
--- /dev/null
+++ b/fs/notify/dnotify/Kconfig
@@ -0,0 +1,10 @@
+config DNOTIFY
+	bool "Dnotify support"
+	default y
+	help
+	  Dnotify is a directory-based per-fd file change notification system
+	  that uses signals to communicate events to user-space.  There exist
+	  superior alternatives, but some applications may still rely on
+	  dnotify.
+
+	  If unsure, say Y.
diff --git a/fs/notify/dnotify/Makefile b/fs/notify/dnotify/Makefile
new file mode 100644
index 000000000000..f145251dcadb
--- /dev/null
+++ b/fs/notify/dnotify/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_DNOTIFY)		+= dnotify.o
diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
new file mode 100644
index 000000000000..b0aa2cde80bd
--- /dev/null
+++ b/fs/notify/dnotify/dnotify.c
@@ -0,0 +1,191 @@
+/*
+ * Directory notifications for Linux.
+ *
+ * Copyright (C) 2000,2001,2002 Stephen Rothwell
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/dnotify.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/slab.h>
+#include <linux/fdtable.h>
+
+int dir_notify_enable __read_mostly = 1;
+
+static struct kmem_cache *dn_cache __read_mostly;
+
+static void redo_inode_mask(struct inode *inode)
+{
+	unsigned long new_mask;
+	struct dnotify_struct *dn;
+
+	new_mask = 0;
+	for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next)
+		new_mask |= dn->dn_mask & ~DN_MULTISHOT;
+	inode->i_dnotify_mask = new_mask;
+}
+
+void dnotify_flush(struct file *filp, fl_owner_t id)
+{
+	struct dnotify_struct *dn;
+	struct dnotify_struct **prev;
+	struct inode *inode;
+
+	inode = filp->f_path.dentry->d_inode;
+	if (!S_ISDIR(inode->i_mode))
+		return;
+	spin_lock(&inode->i_lock);
+	prev = &inode->i_dnotify;
+	while ((dn = *prev) != NULL) {
+		if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
+			*prev = dn->dn_next;
+			redo_inode_mask(inode);
+			kmem_cache_free(dn_cache, dn);
+			break;
+		}
+		prev = &dn->dn_next;
+	}
+	spin_unlock(&inode->i_lock);
+}
+
+int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
+{
+	struct dnotify_struct *dn;
+	struct dnotify_struct *odn;
+	struct dnotify_struct **prev;
+	struct inode *inode;
+	fl_owner_t id = current->files;
+	struct file *f;
+	int error = 0;
+
+	if ((arg & ~DN_MULTISHOT) == 0) {
+		dnotify_flush(filp, id);
+		return 0;
+	}
+	if (!dir_notify_enable)
+		return -EINVAL;
+	inode = filp->f_path.dentry->d_inode;
+	if (!S_ISDIR(inode->i_mode))
+		return -ENOTDIR;
+	dn = kmem_cache_alloc(dn_cache, GFP_KERNEL);
+	if (dn == NULL)
+		return -ENOMEM;
+	spin_lock(&inode->i_lock);
+	prev = &inode->i_dnotify;
+	while ((odn = *prev) != NULL) {
+		if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
+			odn->dn_fd = fd;
+			odn->dn_mask |= arg;
+			inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
+			goto out_free;
+		}
+		prev = &odn->dn_next;
+	}
+
+	rcu_read_lock();
+	f = fcheck(fd);
+	rcu_read_unlock();
+	/* we'd lost the race with close(), sod off silently */
+	/* note that inode->i_lock prevents reordering problems
+	 * between accesses to descriptor table and ->i_dnotify */
+	if (f != filp)
+		goto out_free;
+
+	error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
+	if (error)
+		goto out_free;
+
+	dn->dn_mask = arg;
+	dn->dn_fd = fd;
+	dn->dn_filp = filp;
+	dn->dn_owner = id;
+	inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
+	dn->dn_next = inode->i_dnotify;
+	inode->i_dnotify = dn;
+	spin_unlock(&inode->i_lock);
+	return 0;
+
+out_free:
+	spin_unlock(&inode->i_lock);
+	kmem_cache_free(dn_cache, dn);
+	return error;
+}
+
+void __inode_dir_notify(struct inode *inode, unsigned long event)
+{
+	struct dnotify_struct *	dn;
+	struct dnotify_struct **prev;
+	struct fown_struct *	fown;
+	int			changed = 0;
+
+	spin_lock(&inode->i_lock);
+	prev = &inode->i_dnotify;
+	while ((dn = *prev) != NULL) {
+		if ((dn->dn_mask & event) == 0) {
+			prev = &dn->dn_next;
+			continue;
+		}
+		fown = &dn->dn_filp->f_owner;
+		send_sigio(fown, dn->dn_fd, POLL_MSG);
+		if (dn->dn_mask & DN_MULTISHOT)
+			prev = &dn->dn_next;
+		else {
+			*prev = dn->dn_next;
+			changed = 1;
+			kmem_cache_free(dn_cache, dn);
+		}
+	}
+	if (changed)
+		redo_inode_mask(inode);
+	spin_unlock(&inode->i_lock);
+}
+
+EXPORT_SYMBOL(__inode_dir_notify);
+
+/*
+ * This is hopelessly wrong, but unfixable without API changes.  At
+ * least it doesn't oops the kernel...
+ *
+ * To safely access ->d_parent we need to keep d_move away from it.  Use the
+ * dentry's d_lock for this.
+ */
+void dnotify_parent(struct dentry *dentry, unsigned long event)
+{
+	struct dentry *parent;
+
+	if (!dir_notify_enable)
+		return;
+
+	spin_lock(&dentry->d_lock);
+	parent = dentry->d_parent;
+	if (parent->d_inode->i_dnotify_mask & event) {
+		dget(parent);
+		spin_unlock(&dentry->d_lock);
+		__inode_dir_notify(parent->d_inode, event);
+		dput(parent);
+	} else {
+		spin_unlock(&dentry->d_lock);
+	}
+}
+EXPORT_SYMBOL_GPL(dnotify_parent);
+
+static int __init dnotify_init(void)
+{
+	dn_cache = kmem_cache_create("dnotify_cache",
+		sizeof(struct dnotify_struct), 0, SLAB_PANIC, NULL);
+	return 0;
+}
+
+module_init(dnotify_init)