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/*

 * 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);

/**

 * 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);

/*

 * 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) {

                                WARN_ON(child->d_flags & DCACHE_INOTIFY_PARENT_WATCHED);

                                continue;

                        }

                        spin_lock(&child->d_lock);

                        if (watched) {

                                WARN_ON(child->d_flags &

                                                DCACHE_INOTIFY_PARENT_WATCHED);

                                child->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;

                        } else {

                                WARN_ON(!(child->d_flags &

                                        DCACHE_INOTIFY_PARENT_WATCHED));

                                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;

        WARN_ON(entry->d_flags & DCACHE_INOTIFY_PARENT_WATCHED);

        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;

                        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);

                }

                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);

/**

 * 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.

         */

        while (1) {

                struct inotify_watch *watch;

                struct list_head *watches;

                struct inode *inode;

                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);

                get_inotify_watch(watch);

                mutex_unlock(&ih->mutex);

                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);

                put_inotify_watch(watch);

        }

        /* 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;

        /* 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);

        if (!inotify_inode_watched(inode))

                set_dentry_child_flags(inode, 1);

        /* Add the watch to the handle's and the inode's list */

        list_add(&watch->h_list, &ih->watches);

        list_add(&watch->i_list, &inode->inotify_watches);

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)

{