1 files changed, 913 insertions, 0 deletions

diff --git a/fs/notify/inotify/inotify.c b/fs/notify/inotify/inotify.c
new file mode 100644
index 000000000000..dae3f28f30d4
--- /dev/null
+++ b/fs/notify/inotify/inotify.c
@@ -0,0 +1,913 @@
+/*
+ * fs/inotify.c - inode-based file event notifications
+ *
+ * Authors:
+ *      John McCutchan  <ttb@tentacle.dhs.org>
+ *      Robert Love     <rml@novell.com>
+ *
+ * Kernel API added by: Amy Griffis <amy.griffis@hp.com>
+ *
+ * Copyright (C) 2005 John McCutchan
+ * Copyright 2006 Hewlett-Packard Development Company, L.P.
+ *
+ * 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/module.h>
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/idr.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/writeback.h>
+#include <linux/inotify.h>
+
+static atomic_t inotify_cookie;
+
+/*
+ * Lock ordering:
+ *
+ * dentry->d_lock (used to keep d_move() away from dentry->d_parent)
+ * iprune_mutex (synchronize shrink_icache_memory())
+ *      inode_lock (protects the super_block->s_inodes list)
+ *      inode->inotify_mutex (protects inode->inotify_watches and watches->i_list)
+ *              inotify_handle->mutex (protects inotify_handle and watches->h_list)
+ *
+ * The inode->inotify_mutex and inotify_handle->mutex and held during execution
+ * of a caller's event handler.  Thus, the caller must not hold any locks
+ * taken in their event handler while calling any of the published inotify
+ * interfaces.
+ */
+
+/*
+ * Lifetimes of the three main data structures--inotify_handle, inode, and
+ * inotify_watch--are managed by reference count.
+ *
+ * inotify_handle: Lifetime is from inotify_init() to inotify_destroy().
+ * Additional references can bump the count via get_inotify_handle() and drop
+ * the count via put_inotify_handle().
+ *
+ * inotify_watch: for inotify's purposes, lifetime is from inotify_add_watch()
+ * to remove_watch_no_event().  Additional references can bump the count via
+ * get_inotify_watch() and drop the count via put_inotify_watch().  The caller
+ * is reponsible for the final put after receiving IN_IGNORED, or when using
+ * IN_ONESHOT after receiving the first event.  Inotify does the final put if
+ * inotify_destroy() is called.
+ *
+ * inode: Pinned so long as the inode is associated with a watch, from
+ * inotify_add_watch() to the final put_inotify_watch().
+ */
+
+/*
+ * struct inotify_handle - represents an inotify instance
+ *
+ * This structure is protected by the mutex 'mutex'.
+ */
+struct inotify_handle {
+        struct idr              idr;            /* idr mapping wd -> watch */
+        struct mutex            mutex;          /* protects this bad boy */
+        struct list_head        watches;        /* list of watches */
+        atomic_t                count;          /* reference count */
+        u32                     last_wd;        /* the last wd allocated */
+        const struct inotify_operations *in_ops; /* inotify caller operations */
+};
+
+static inline void get_inotify_handle(struct inotify_handle *ih)
+{
+        atomic_inc(&ih->count);
+}
+
+static inline void put_inotify_handle(struct inotify_handle *ih)
+{
+        if (atomic_dec_and_test(&ih->count)) {
+                idr_destroy(&ih->idr);
+                kfree(ih);
+        }
+}
+
+/**
+ * get_inotify_watch - grab a reference to an inotify_watch
+ * @watch: watch to grab
+ */
+void get_inotify_watch(struct inotify_watch *watch)
+{
+        atomic_inc(&watch->count);
+}
+EXPORT_SYMBOL_GPL(get_inotify_watch);
+
+int pin_inotify_watch(struct inotify_watch *watch)
+{
+        struct super_block *sb = watch->inode->i_sb;
+        spin_lock(&sb_lock);
+        if (sb->s_count >= S_BIAS) {
+                atomic_inc(&sb->s_active);
+                spin_unlock(&sb_lock);
+                atomic_inc(&watch->count);
+                return 1;
+        }
+        spin_unlock(&sb_lock);
+        return 0;
+}
+
+/**
+ * put_inotify_watch - decrements the ref count on a given watch.  cleans up
+ * watch references if the count reaches zero.  inotify_watch is freed by
+ * inotify callers via the destroy_watch() op.
+ * @watch: watch to release
+ */
+void put_inotify_watch(struct inotify_watch *watch)
+{
+        if (atomic_dec_and_test(&watch->count)) {
+                struct inotify_handle *ih = watch->ih;
+
+                iput(watch->inode);
+                ih->in_ops->destroy_watch(watch);
+                put_inotify_handle(ih);
+        }
+}
+EXPORT_SYMBOL_GPL(put_inotify_watch);
+
+void unpin_inotify_watch(struct inotify_watch *watch)
+{
+        struct super_block *sb = watch->inode->i_sb;
+        put_inotify_watch(watch);
+        deactivate_super(sb);
+}
+
+/*
+ * inotify_handle_get_wd - returns the next WD for use by the given handle
+ *
+ * Callers must hold ih->mutex.  This function can sleep.
+ */
+static int inotify_handle_get_wd(struct inotify_handle *ih,
+                                 struct inotify_watch *watch)
+{
+        int ret;
+
+        do {
+                if (unlikely(!idr_pre_get(&ih->idr, GFP_KERNEL)))
+                        return -ENOSPC;
+                ret = idr_get_new_above(&ih->idr, watch, ih->last_wd+1, &watch->wd);
+        } while (ret == -EAGAIN);
+
+        if (likely(!ret))
+                ih->last_wd = watch->wd;
+
+        return ret;
+}
+
+/*
+ * inotify_inode_watched - returns nonzero if there are watches on this inode
+ * and zero otherwise.  We call this lockless, we do not care if we race.
+ */
+static inline int inotify_inode_watched(struct inode *inode)
+{
+        return !list_empty(&inode->inotify_watches);
+}
+
+/*
+ * Get child dentry flag into synch with parent inode.
+ * Flag should always be clear for negative dentrys.
+ */
+static void set_dentry_child_flags(struct inode *inode, int watched)
+{
+        struct dentry *alias;
+
+        spin_lock(&dcache_lock);
+        list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+                struct dentry *child;
+
+                list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
+                        if (!child->d_inode)
+                                continue;
+
+                        spin_lock(&child->d_lock);
+                        if (watched)
+                                child->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
+                        else
+                                child->d_flags &=~DCACHE_INOTIFY_PARENT_WATCHED;
+                        spin_unlock(&child->d_lock);
+                }
+        }
+        spin_unlock(&dcache_lock);
+}
+
+/*
+ * inotify_find_handle - find the watch associated with the given inode and
+ * handle
+ *
+ * Callers must hold inode->inotify_mutex.
+ */
+static struct inotify_watch *inode_find_handle(struct inode *inode,
+                                               struct inotify_handle *ih)
+{
+        struct inotify_watch *watch;
+
+        list_for_each_entry(watch, &inode->inotify_watches, i_list) {
+                if (watch->ih == ih)
+                        return watch;
+        }
+
+        return NULL;
+}
+
+/*
+ * remove_watch_no_event - remove watch without the IN_IGNORED event.
+ *
+ * Callers must hold both inode->inotify_mutex and ih->mutex.
+ */
+static void remove_watch_no_event(struct inotify_watch *watch,
+                                  struct inotify_handle *ih)
+{
+        list_del(&watch->i_list);
+        list_del(&watch->h_list);
+
+        if (!inotify_inode_watched(watch->inode))
+                set_dentry_child_flags(watch->inode, 0);
+
+        idr_remove(&ih->idr, watch->wd);
+}
+
+/**
+ * inotify_remove_watch_locked - Remove a watch from both the handle and the
+ * inode.  Sends the IN_IGNORED event signifying that the inode is no longer
+ * watched.  May be invoked from a caller's event handler.
+ * @ih: inotify handle associated with watch
+ * @watch: watch to remove
+ *
+ * Callers must hold both inode->inotify_mutex and ih->mutex.
+ */
+void inotify_remove_watch_locked(struct inotify_handle *ih,
+                                 struct inotify_watch *watch)
+{
+        remove_watch_no_event(watch, ih);
+        ih->in_ops->handle_event(watch, watch->wd, IN_IGNORED, 0, NULL, NULL);
+}
+EXPORT_SYMBOL_GPL(inotify_remove_watch_locked);
+
+/* Kernel API for producing events */
+
+/*
+ * inotify_d_instantiate - instantiate dcache entry for inode
+ */
+void inotify_d_instantiate(struct dentry *entry, struct inode *inode)
+{
+        struct dentry *parent;
+
+        if (!inode)
+                return;
+
+        spin_lock(&entry->d_lock);
+        parent = entry->d_parent;
+        if (parent->d_inode && inotify_inode_watched(parent->d_inode))
+                entry->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
+        spin_unlock(&entry->d_lock);
+}
+
+/*
+ * inotify_d_move - dcache entry has been moved
+ */
+void inotify_d_move(struct dentry *entry)
+{
+        struct dentry *parent;
+
+        parent = entry->d_parent;
+        if (inotify_inode_watched(parent->d_inode))
+                entry->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
+        else
+                entry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED;
+}
+
+/**
+ * inotify_inode_queue_event - queue an event to all watches on this inode
+ * @inode: inode event is originating from
+ * @mask: event mask describing this event
+ * @cookie: cookie for synchronization, or zero
+ * @name: filename, if any
+ * @n_inode: inode associated with name
+ */
+void inotify_inode_queue_event(struct inode *inode, u32 mask, u32 cookie,
+                               const char *name, struct inode *n_inode)
+{
+        struct inotify_watch *watch, *next;
+
+        if (!inotify_inode_watched(inode))
+                return;
+
+        mutex_lock(&inode->inotify_mutex);
+        list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
+                u32 watch_mask = watch->mask;
+                if (watch_mask & mask) {
+                        struct inotify_handle *ih= watch->ih;
+                        mutex_lock(&ih->mutex);
+                        if (watch_mask & IN_ONESHOT)
+                                remove_watch_no_event(watch, ih);
+                        ih->in_ops->handle_event(watch, watch->wd, mask, cookie,
+                                                 name, n_inode);
+                        mutex_unlock(&ih->mutex);
+                }
+        }
+        mutex_unlock(&inode->inotify_mutex);
+}
+EXPORT_SYMBOL_GPL(inotify_inode_queue_event);
+
+/**
+ * inotify_dentry_parent_queue_event - queue an event to a dentry's parent
+ * @dentry: the dentry in question, we queue against this dentry's parent
+ * @mask: event mask describing this event
+ * @cookie: cookie for synchronization, or zero
+ * @name: filename, if any
+ */
+void inotify_dentry_parent_queue_event(struct dentry *dentry, u32 mask,
+                                       u32 cookie, const char *name)
+{
+        struct dentry *parent;
+        struct inode *inode;
+
+        if (!(dentry->d_flags & DCACHE_INOTIFY_PARENT_WATCHED))
+                return;
+
+        spin_lock(&dentry->d_lock);
+        parent = dentry->d_parent;
+        inode = parent->d_inode;
+
+        if (inotify_inode_watched(inode)) {
+                dget(parent);
+                spin_unlock(&dentry->d_lock);
+                inotify_inode_queue_event(inode, mask, cookie, name,
+                                          dentry->d_inode);
+                dput(parent);
+        } else
+                spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL_GPL(inotify_dentry_parent_queue_event);
+
+/**
+ * inotify_get_cookie - return a unique cookie for use in synchronizing events.
+ */
+u32 inotify_get_cookie(void)
+{
+        return atomic_inc_return(&inotify_cookie);
+}
+EXPORT_SYMBOL_GPL(inotify_get_cookie);
+
+/**
+ * inotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
+ * @list: list of inodes being unmounted (sb->s_inodes)
+ *
+ * Called with inode_lock held, protecting the unmounting super block's list
+ * of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
+ * We temporarily drop inode_lock, however, and CAN block.
+ */
+void inotify_unmount_inodes(struct list_head *list)
+{
+        struct inode *inode, *next_i, *need_iput = NULL;
+
+        list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
+                struct inotify_watch *watch, *next_w;
+                struct inode *need_iput_tmp;
+                struct list_head *watches;
+
+                /*
+                 * If i_count is zero, the inode cannot have any watches and
+                 * doing an __iget/iput with MS_ACTIVE clear would actually
+                 * evict all inodes with zero i_count from icache which is
+                 * unnecessarily violent and may in fact be illegal to do.
+                 */
+                if (!atomic_read(&inode->i_count))
+                        continue;
+
+                /*
+                 * We cannot __iget() an inode in state I_CLEAR, I_FREEING, or
+                 * I_WILL_FREE which is fine because by that point the inode
+                 * cannot have any associated watches.
+                 */
+                if (inode->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))
+                        continue;
+
+                need_iput_tmp = need_iput;
+                need_iput = NULL;
+                /* In case inotify_remove_watch_locked() drops a reference. */
+                if (inode != need_iput_tmp)
+                        __iget(inode);
+                else
+                        need_iput_tmp = NULL;
+                /* In case the dropping of a reference would nuke next_i. */
+                if ((&next_i->i_sb_list != list) &&
+                                atomic_read(&next_i->i_count) &&
+                                !(next_i->i_state & (I_CLEAR | I_FREEING |
+                                        I_WILL_FREE))) {
+                        __iget(next_i);
+                        need_iput = next_i;
+                }
+
+                /*
+                 * We can safely drop inode_lock here because we hold
+                 * references on both inode and next_i.  Also no new inodes
+                 * will be added since the umount has begun.  Finally,
+                 * iprune_mutex keeps shrink_icache_memory() away.
+                 */
+                spin_unlock(&inode_lock);
+
+                if (need_iput_tmp)
+                        iput(need_iput_tmp);
+
+                /* for each watch, send IN_UNMOUNT and then remove it */
+                mutex_lock(&inode->inotify_mutex);
+                watches = &inode->inotify_watches;
+                list_for_each_entry_safe(watch, next_w, watches, i_list) {
+                        struct inotify_handle *ih= watch->ih;
+                        get_inotify_watch(watch);
+                        mutex_lock(&ih->mutex);
+                        ih->in_ops->handle_event(watch, watch->wd, IN_UNMOUNT, 0,
+                                                 NULL, NULL);
+                        inotify_remove_watch_locked(ih, watch);
+                        mutex_unlock(&ih->mutex);
+                        put_inotify_watch(watch);
+                }
+                mutex_unlock(&inode->inotify_mutex);
+                iput(inode);            
+
+                spin_lock(&inode_lock);
+        }
+}
+EXPORT_SYMBOL_GPL(inotify_unmount_inodes);
+
+/**
+ * inotify_inode_is_dead - an inode has been deleted, cleanup any watches
+ * @inode: inode that is about to be removed
+ */
+void inotify_inode_is_dead(struct inode *inode)
+{
+        struct inotify_watch *watch, *next;
+
+        mutex_lock(&inode->inotify_mutex);
+        list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
+                struct inotify_handle *ih = watch->ih;
+                mutex_lock(&ih->mutex);
+                inotify_remove_watch_locked(ih, watch);
+                mutex_unlock(&ih->mutex);
+        }
+        mutex_unlock(&inode->inotify_mutex);
+}
+EXPORT_SYMBOL_GPL(inotify_inode_is_dead);
+
+/* Kernel Consumer API */
+
+/**
+ * inotify_init - allocate and initialize an inotify instance
+ * @ops: caller's inotify operations
+ */
+struct inotify_handle *inotify_init(const struct inotify_operations *ops)
+{
+        struct inotify_handle *ih;
+
+        ih = kmalloc(sizeof(struct inotify_handle), GFP_KERNEL);
+        if (unlikely(!ih))
+                return ERR_PTR(-ENOMEM);
+
+        idr_init(&ih->idr);
+        INIT_LIST_HEAD(&ih->watches);
+        mutex_init(&ih->mutex);
+        ih->last_wd = 0;
+        ih->in_ops = ops;
+        atomic_set(&ih->count, 0);
+        get_inotify_handle(ih);
+
+        return ih;
+}
+EXPORT_SYMBOL_GPL(inotify_init);
+
+/**
+ * inotify_init_watch - initialize an inotify watch
+ * @watch: watch to initialize
+ */
+void inotify_init_watch(struct inotify_watch *watch)
+{
+        INIT_LIST_HEAD(&watch->h_list);
+        INIT_LIST_HEAD(&watch->i_list);
+        atomic_set(&watch->count, 0);
+        get_inotify_watch(watch); /* initial get */
+}
+EXPORT_SYMBOL_GPL(inotify_init_watch);
+
+/*
+ * Watch removals suck violently.  To kick the watch out we need (in this
+ * order) inode->inotify_mutex and ih->mutex.  That's fine if we have
+ * a hold on inode; however, for all other cases we need to make damn sure
+ * we don't race with umount.  We can *NOT* just grab a reference to a
+ * watch - inotify_unmount_inodes() will happily sail past it and we'll end
+ * with reference to inode potentially outliving its superblock.  Ideally
+ * we just want to grab an active reference to superblock if we can; that
+ * will make sure we won't go into inotify_umount_inodes() until we are
+ * done.  Cleanup is just deactivate_super().  However, that leaves a messy
+ * case - what if we *are* racing with umount() and active references to
+ * superblock can't be acquired anymore?  We can bump ->s_count, grab
+ * ->s_umount, which will almost certainly wait until the superblock is shut
+ * down and the watch in question is pining for fjords.  That's fine, but
+ * there is a problem - we might have hit the window between ->s_active
+ * getting to 0 / ->s_count - below S_BIAS (i.e. the moment when superblock
+ * is past the point of no return and is heading for shutdown) and the
+ * moment when deactivate_super() acquires ->s_umount.  We could just do
+ * drop_super() yield() and retry, but that's rather antisocial and this
+ * stuff is luser-triggerable.  OTOH, having grabbed ->s_umount and having
+ * found that we'd got there first (i.e. that ->s_root is non-NULL) we know
+ * that we won't race with inotify_umount_inodes().  So we could grab a
+ * reference to watch and do the rest as above, just with drop_super() instead
+ * of deactivate_super(), right?  Wrong.  We had to drop ih->mutex before we
+ * could grab ->s_umount.  So the watch could've been gone already.
+ *
+ * That still can be dealt with - we need to save watch->wd, do idr_find()
+ * and compare its result with our pointer.  If they match, we either have
+ * the damn thing still alive or we'd lost not one but two races at once,
+ * the watch had been killed and a new one got created with the same ->wd
+ * at the same address.  That couldn't have happened in inotify_destroy(),
+ * but inotify_rm_wd() could run into that.  Still, "new one got created"
+ * is not a problem - we have every right to kill it or leave it alone,
+ * whatever's more convenient.
+ *
+ * So we can use idr_find(...) == watch && watch->inode->i_sb == sb as
+ * "grab it and kill it" check.  If it's been our original watch, we are
+ * fine, if it's a newcomer - nevermind, just pretend that we'd won the
+ * race and kill the fscker anyway; we are safe since we know that its
+ * superblock won't be going away.
+ *
+ * And yes, this is far beyond mere "not very pretty"; so's the entire
+ * concept of inotify to start with.
+ */
+
+/**
+ * pin_to_kill - pin the watch down for removal
+ * @ih: inotify handle
+ * @watch: watch to kill
+ *
+ * Called with ih->mutex held, drops it.  Possible return values:
+ * 0 - nothing to do, it has died
+ * 1 - remove it, drop the reference and deactivate_super()
+ * 2 - remove it, drop the reference and drop_super(); we tried hard to avoid
+ * that variant, since it involved a lot of PITA, but that's the best that
+ * could've been done.
+ */
+static int pin_to_kill(struct inotify_handle *ih, struct inotify_watch *watch)
+{
+        struct super_block *sb = watch->inode->i_sb;
+        s32 wd = watch->wd;
+
+        spin_lock(&sb_lock);
+        if (sb->s_count >= S_BIAS) {
+                atomic_inc(&sb->s_active);
+                spin_unlock(&sb_lock);
+                get_inotify_watch(watch);
+                mutex_unlock(&ih->mutex);
+                return 1;       /* the best outcome */
+        }
+        sb->s_count++;
+        spin_unlock(&sb_lock);
+        mutex_unlock(&ih->mutex); /* can't grab ->s_umount under it */
+        down_read(&sb->s_umount);
+        if (likely(!sb->s_root)) {
+                /* fs is already shut down; the watch is dead */
+                drop_super(sb);
+                return 0;
+        }
+        /* raced with the final deactivate_super() */
+        mutex_lock(&ih->mutex);
+        if (idr_find(&ih->idr, wd) != watch || watch->inode->i_sb != sb) {
+                /* the watch is dead */
+                mutex_unlock(&ih->mutex);
+                drop_super(sb);
+                return 0;
+        }
+        /* still alive or freed and reused with the same sb and wd; kill */
+        get_inotify_watch(watch);
+        mutex_unlock(&ih->mutex);
+        return 2;
+}
+
+static void unpin_and_kill(struct inotify_watch *watch, int how)
+{
+        struct super_block *sb = watch->inode->i_sb;
+        put_inotify_watch(watch);
+        switch (how) {
+        case 1:
+                deactivate_super(sb);
+                break;
+        case 2:
+                drop_super(sb);
+        }
+}
+
+/**
+ * inotify_destroy - clean up and destroy an inotify instance
+ * @ih: inotify handle
+ */
+void inotify_destroy(struct inotify_handle *ih)
+{
+        /*
+         * Destroy all of the watches for this handle. Unfortunately, not very
+         * pretty.  We cannot do a simple iteration over the list, because we
+         * do not know the inode until we iterate to the watch.  But we need to
+         * hold inode->inotify_mutex before ih->mutex.  The following works.
+         *
+         * AV: it had to become even uglier to start working ;-/
+         */
+        while (1) {
+                struct inotify_watch *watch;
+                struct list_head *watches;
+                struct super_block *sb;
+                struct inode *inode;
+                int how;
+
+                mutex_lock(&ih->mutex);
+                watches = &ih->watches;
+                if (list_empty(watches)) {
+                        mutex_unlock(&ih->mutex);
+                        break;
+                }
+                watch = list_first_entry(watches, struct inotify_watch, h_list);
+                sb = watch->inode->i_sb;
+                how = pin_to_kill(ih, watch);
+                if (!how)
+                        continue;
+
+                inode = watch->inode;
+                mutex_lock(&inode->inotify_mutex);
+                mutex_lock(&ih->mutex);
+
+                /* make sure we didn't race with another list removal */
+                if (likely(idr_find(&ih->idr, watch->wd))) {
+                        remove_watch_no_event(watch, ih);
+                        put_inotify_watch(watch);
+                }
+
+                mutex_unlock(&ih->mutex);
+                mutex_unlock(&inode->inotify_mutex);
+                unpin_and_kill(watch, how);
+        }
+
+        /* free this handle: the put matching the get in inotify_init() */
+        put_inotify_handle(ih);
+}
+EXPORT_SYMBOL_GPL(inotify_destroy);
+
+/**
+ * inotify_find_watch - find an existing watch for an (ih,inode) pair
+ * @ih: inotify handle
+ * @inode: inode to watch
+ * @watchp: pointer to existing inotify_watch
+ *
+ * Caller must pin given inode (via nameidata).
+ */
+s32 inotify_find_watch(struct inotify_handle *ih, struct inode *inode,
+                       struct inotify_watch **watchp)
+{
+        struct inotify_watch *old;
+        int ret = -ENOENT;
+
+        mutex_lock(&inode->inotify_mutex);
+        mutex_lock(&ih->mutex);
+
+        old = inode_find_handle(inode, ih);
+        if (unlikely(old)) {
+                get_inotify_watch(old); /* caller must put watch */
+                *watchp = old;
+                ret = old->wd;
+        }
+
+        mutex_unlock(&ih->mutex);
+        mutex_unlock(&inode->inotify_mutex);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(inotify_find_watch);
+
+/**
+ * inotify_find_update_watch - find and update the mask of an existing watch
+ * @ih: inotify handle
+ * @inode: inode's watch to update
+ * @mask: mask of events to watch
+ *
+ * Caller must pin given inode (via nameidata).
+ */
+s32 inotify_find_update_watch(struct inotify_handle *ih, struct inode *inode,
+                              u32 mask)
+{
+        struct inotify_watch *old;
+        int mask_add = 0;
+        int ret;
+
+        if (mask & IN_MASK_ADD)
+                mask_add = 1;
+
+        /* don't allow invalid bits: we don't want flags set */
+        mask &= IN_ALL_EVENTS | IN_ONESHOT;
+        if (unlikely(!mask))
+                return -EINVAL;
+
+        mutex_lock(&inode->inotify_mutex);
+        mutex_lock(&ih->mutex);
+
+        /*
+         * Handle the case of re-adding a watch on an (inode,ih) pair that we
+         * are already watching.  We just update the mask and return its wd.
+         */
+        old = inode_find_handle(inode, ih);
+        if (unlikely(!old)) {
+                ret = -ENOENT;
+                goto out;
+        }
+
+        if (mask_add)
+                old->mask |= mask;
+        else
+                old->mask = mask;
+        ret = old->wd;
+out:
+        mutex_unlock(&ih->mutex);
+        mutex_unlock(&inode->inotify_mutex);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(inotify_find_update_watch);
+
+/**
+ * inotify_add_watch - add a watch to an inotify instance
+ * @ih: inotify handle
+ * @watch: caller allocated watch structure
+ * @inode: inode to watch
+ * @mask: mask of events to watch
+ *
+ * Caller must pin given inode (via nameidata).
+ * Caller must ensure it only calls inotify_add_watch() once per watch.
+ * Calls inotify_handle_get_wd() so may sleep.
+ */
+s32 inotify_add_watch(struct inotify_handle *ih, struct inotify_watch *watch,
+                      struct inode *inode, u32 mask)
+{
+        int ret = 0;
+        int newly_watched;
+
+        /* don't allow invalid bits: we don't want flags set */
+        mask &= IN_ALL_EVENTS | IN_ONESHOT;
+        if (unlikely(!mask))
+                return -EINVAL;
+        watch->mask = mask;
+
+        mutex_lock(&inode->inotify_mutex);
+        mutex_lock(&ih->mutex);
+
+        /* Initialize a new watch */
+        ret = inotify_handle_get_wd(ih, watch);
+        if (unlikely(ret))
+                goto out;
+        ret = watch->wd;
+
+        /* save a reference to handle and bump the count to make it official */
+        get_inotify_handle(ih);
+        watch->ih = ih;
+
+        /*
+         * Save a reference to the inode and bump the ref count to make it
+         * official.  We hold a reference to nameidata, which makes this safe.
+         */
+        watch->inode = igrab(inode);
+
+        /* Add the watch to the handle's and the inode's list */
+        newly_watched = !inotify_inode_watched(inode);
+        list_add(&watch->h_list, &ih->watches);
+        list_add(&watch->i_list, &inode->inotify_watches);
+        /*
+         * Set child flags _after_ adding the watch, so there is no race
+         * windows where newly instantiated children could miss their parent's
+         * watched flag.
+         */
+        if (newly_watched)
+                set_dentry_child_flags(inode, 1);
+
+out:
+        mutex_unlock(&ih->mutex);
+        mutex_unlock(&inode->inotify_mutex);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(inotify_add_watch);
+
+/**
+ * inotify_clone_watch - put the watch next to existing one
+ * @old: already installed watch
+ * @new: new watch
+ *
+ * Caller must hold the inotify_mutex of inode we are dealing with;
+ * it is expected to remove the old watch before unlocking the inode.
+ */
+s32 inotify_clone_watch(struct inotify_watch *old, struct inotify_watch *new)
+{
+        struct inotify_handle *ih = old->ih;
+        int ret = 0;
+
+        new->mask = old->mask;
+        new->ih = ih;
+
+        mutex_lock(&ih->mutex);
+
+        /* Initialize a new watch */
+        ret = inotify_handle_get_wd(ih, new);
+        if (unlikely(ret))
+                goto out;
+        ret = new->wd;
+
+        get_inotify_handle(ih);
+
+        new->inode = igrab(old->inode);
+
+        list_add(&new->h_list, &ih->watches);
+        list_add(&new->i_list, &old->inode->inotify_watches);
+out:
+        mutex_unlock(&ih->mutex);
+        return ret;
+}
+
+void inotify_evict_watch(struct inotify_watch *watch)
+{
+        get_inotify_watch(watch);
+        mutex_lock(&watch->ih->mutex);
+        inotify_remove_watch_locked(watch->ih, watch);
+        mutex_unlock(&watch->ih->mutex);
+}
+
+/**
+ * inotify_rm_wd - remove a watch from an inotify instance
+ * @ih: inotify handle
+ * @wd: watch descriptor to remove
+ *
+ * Can sleep.
+ */
+int inotify_rm_wd(struct inotify_handle *ih, u32 wd)
+{
+        struct inotify_watch *watch;
+        struct super_block *sb;
+        struct inode *inode;
+        int how;
+
+        mutex_lock(&ih->mutex);
+        watch = idr_find(&ih->idr, wd);
+        if (unlikely(!watch)) {
+                mutex_unlock(&ih->mutex);
+                return -EINVAL;
+        }
+        sb = watch->inode->i_sb;
+        how = pin_to_kill(ih, watch);
+        if (!how)
+                return 0;
+
+        inode = watch->inode;
+
+        mutex_lock(&inode->inotify_mutex);
+        mutex_lock(&ih->mutex);
+
+        /* make sure that we did not race */
+        if (likely(idr_find(&ih->idr, wd) == watch))
+                inotify_remove_watch_locked(ih, watch);
+
+        mutex_unlock(&ih->mutex);
+        mutex_unlock(&inode->inotify_mutex);
+        unpin_and_kill(watch, how);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(inotify_rm_wd);
+
+/**
+ * inotify_rm_watch - remove a watch from an inotify instance
+ * @ih: inotify handle
+ * @watch: watch to remove
+ *
+ * Can sleep.
+ */
+int inotify_rm_watch(struct inotify_handle *ih,
+                     struct inotify_watch *watch)
+{
+        return inotify_rm_wd(ih, watch->wd);
+}
+EXPORT_SYMBOL_GPL(inotify_rm_watch);
+
+/*
+ * inotify_setup - core initialization function
+ */
+static int __init inotify_setup(void)
+{
+        atomic_set(&inotify_cookie, 0);
+
+        return 0;
+}
+
+module_init(inotify_setup);