3 files changed, 202 insertions, 0 deletions

diff --git a/fs/notify/dnotify/Kconfig b/fs/notify/dnotify/Kconfig
new file mode 100644
index 00000000000..26adf5dfa64
--- /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 00000000000..f145251dcad
--- /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 00000000000..b0aa2cde80b
--- /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)