filesystem notification: create fs/notify to contain all fs notification

Creating a generic filesystem notification interface, fsnotify, which will be
used by inotify, dnotify, and eventually fanotify is really starting to
clutter the fs directory.  This patch simply moves inotify and dnotify into
fs/notify/inotify and fs/notify/dnotify respectively to make both current fs/
and future notification tidier.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

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)