diff options
Diffstat (limited to 'fs/inotify.c')
| -rw-r--r-- | fs/inotify.c | 999 |
1 files changed, 999 insertions, 0 deletions
diff --git a/fs/inotify.c b/fs/inotify.c new file mode 100644 index 000000000000..e423bfe0c86f --- /dev/null +++ b/fs/inotify.c @@ -0,0 +1,999 @@ +/* + * fs/inotify.c - inode-based file event notifications + * + * Authors: + * John McCutchan <ttb@tentacle.dhs.org> + * Robert Love <rml@novell.com> + * + * Copyright (C) 2005 John McCutchan + * + * 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/sched.h> +#include <linux/spinlock.h> +#include <linux/idr.h> +#include <linux/slab.h> +#include <linux/fs.h> +#include <linux/file.h> +#include <linux/mount.h> +#include <linux/namei.h> +#include <linux/poll.h> +#include <linux/device.h> +#include <linux/miscdevice.h> +#include <linux/init.h> +#include <linux/list.h> +#include <linux/writeback.h> +#include <linux/inotify.h> + +#include <asm/ioctls.h> + +static atomic_t inotify_cookie; + +static kmem_cache_t *watch_cachep; +static kmem_cache_t *event_cachep; + +static struct vfsmount *inotify_mnt; + +/* These are configurable via /proc/sys/inotify */ +int inotify_max_user_devices; +int inotify_max_user_watches; +int inotify_max_queued_events; + +/* + * Lock ordering: + * + * dentry->d_lock (used to keep d_move() away from dentry->d_parent) + * iprune_sem (synchronize shrink_icache_memory()) + * inode_lock (protects the super_block->s_inodes list) + * inode->inotify_sem (protects inode->inotify_watches and watches->i_list) + * inotify_dev->sem (protects inotify_device and watches->d_list) + */ + +/* + * Lifetimes of the three main data structures--inotify_device, inode, and + * inotify_watch--are managed by reference count. + * + * inotify_device: Lifetime is from open until release. Additional references + * can bump the count via get_inotify_dev() and drop the count via + * put_inotify_dev(). + * + * inotify_watch: Lifetime is from create_watch() to destory_watch(). + * Additional references can bump the count via get_inotify_watch() and drop + * the count via put_inotify_watch(). + * + * inode: Pinned so long as the inode is associated with a watch, from + * create_watch() to put_inotify_watch(). + */ + +/* + * struct inotify_device - represents an open instance of an inotify device + * + * This structure is protected by the semaphore 'sem'. + */ +struct inotify_device { + wait_queue_head_t wq; /* wait queue for i/o */ + struct idr idr; /* idr mapping wd -> watch */ + struct semaphore sem; /* protects this bad boy */ + struct list_head events; /* list of queued events */ + struct list_head watches; /* list of watches */ + atomic_t count; /* reference count */ + struct user_struct *user; /* user who opened this dev */ + unsigned int queue_size; /* size of the queue (bytes) */ + unsigned int event_count; /* number of pending events */ + unsigned int max_events; /* maximum number of events */ +}; + +/* + * struct inotify_kernel_event - An inotify event, originating from a watch and + * queued for user-space. A list of these is attached to each instance of the + * device. In read(), this list is walked and all events that can fit in the + * buffer are returned. + * + * Protected by dev->sem of the device in which we are queued. + */ +struct inotify_kernel_event { + struct inotify_event event; /* the user-space event */ + struct list_head list; /* entry in inotify_device's list */ + char *name; /* filename, if any */ +}; + +/* + * struct inotify_watch - represents a watch request on a specific inode + * + * d_list is protected by dev->sem of the associated watch->dev. + * i_list and mask are protected by inode->inotify_sem of the associated inode. + * dev, inode, and wd are never written to once the watch is created. + */ +struct inotify_watch { + struct list_head d_list; /* entry in inotify_device's list */ + struct list_head i_list; /* entry in inode's list */ + atomic_t count; /* reference count */ + struct inotify_device *dev; /* associated device */ + struct inode *inode; /* associated inode */ + s32 wd; /* watch descriptor */ + u32 mask; /* event mask for this watch */ +}; + +static inline void get_inotify_dev(struct inotify_device *dev) +{ + atomic_inc(&dev->count); +} + +static inline void put_inotify_dev(struct inotify_device *dev) +{ + if (atomic_dec_and_test(&dev->count)) { + atomic_dec(&dev->user->inotify_devs); + free_uid(dev->user); + kfree(dev); + } +} + +static inline void get_inotify_watch(struct inotify_watch *watch) +{ + atomic_inc(&watch->count); +} + +/* + * put_inotify_watch - decrements the ref count on a given watch. cleans up + * the watch and its references if the count reaches zero. + */ +static inline void put_inotify_watch(struct inotify_watch *watch) +{ + if (atomic_dec_and_test(&watch->count)) { + put_inotify_dev(watch->dev); + iput(watch->inode); + kmem_cache_free(watch_cachep, watch); + } +} + +/* + * kernel_event - create a new kernel event with the given parameters + * + * This function can sleep. + */ +static struct inotify_kernel_event * kernel_event(s32 wd, u32 mask, u32 cookie, + const char *name) +{ + struct inotify_kernel_event *kevent; + + kevent = kmem_cache_alloc(event_cachep, GFP_KERNEL); + if (unlikely(!kevent)) + return NULL; + + /* we hand this out to user-space, so zero it just in case */ + memset(&kevent->event, 0, sizeof(struct inotify_event)); + + kevent->event.wd = wd; + kevent->event.mask = mask; + kevent->event.cookie = cookie; + + INIT_LIST_HEAD(&kevent->list); + + if (name) { + size_t len, rem, event_size = sizeof(struct inotify_event); + + /* + * We need to pad the filename so as to properly align an + * array of inotify_event structures. Because the structure is + * small and the common case is a small filename, we just round + * up to the next multiple of the structure's sizeof. This is + * simple and safe for all architectures. + */ + len = strlen(name) + 1; + rem = event_size - len; + if (len > event_size) { + rem = event_size - (len % event_size); + if (len % event_size == 0) + rem = 0; + } + + kevent->name = kmalloc(len + rem, GFP_KERNEL); + if (unlikely(!kevent->name)) { + kmem_cache_free(event_cachep, kevent); + return NULL; + } + memcpy(kevent->name, name, len); + if (rem) + memset(kevent->name + len, 0, rem); + kevent->event.len = len + rem; + } else { + kevent->event.len = 0; + kevent->name = NULL; + } + + return kevent; +} + +/* + * inotify_dev_get_event - return the next event in the given dev's queue + * + * Caller must hold dev->sem. + */ +static inline struct inotify_kernel_event * +inotify_dev_get_event(struct inotify_device *dev) +{ + return list_entry(dev->events.next, struct inotify_kernel_event, list); +} + +/* + * inotify_dev_queue_event - add a new event to the given device + * + * Caller must hold dev->sem. Can sleep (calls kernel_event()). + */ +static void inotify_dev_queue_event(struct inotify_device *dev, + struct inotify_watch *watch, u32 mask, + u32 cookie, const char *name) +{ + struct inotify_kernel_event *kevent, *last; + + /* coalescing: drop this event if it is a dupe of the previous */ + last = inotify_dev_get_event(dev); + if (last && last->event.mask == mask && last->event.wd == watch->wd && + last->event.cookie == cookie) { + const char *lastname = last->name; + + if (!name && !lastname) + return; + if (name && lastname && !strcmp(lastname, name)) + return; + } + + /* the queue overflowed and we already sent the Q_OVERFLOW event */ + if (unlikely(dev->event_count > dev->max_events)) + return; + + /* if the queue overflows, we need to notify user space */ + if (unlikely(dev->event_count == dev->max_events)) + kevent = kernel_event(-1, IN_Q_OVERFLOW, cookie, NULL); + else + kevent = kernel_event(watch->wd, mask, cookie, name); + + if (unlikely(!kevent)) + return; + + /* queue the event and wake up anyone waiting */ + dev->event_count++; + dev->queue_size += sizeof(struct inotify_event) + kevent->event.len; + list_add_tail(&kevent->list, &dev->events); + wake_up_interruptible(&dev->wq); +} + +/* + * remove_kevent - cleans up and ultimately frees the given kevent + * + * Caller must hold dev->sem. + */ +static void remove_kevent(struct inotify_device *dev, + struct inotify_kernel_event *kevent) +{ + list_del(&kevent->list); + + dev->event_count--; + dev->queue_size -= sizeof(struct inotify_event) + kevent->event.len; + + kfree(kevent->name); + kmem_cache_free(event_cachep, kevent); +} + +/* + * inotify_dev_event_dequeue - destroy an event on the given device + * + * Caller must hold dev->sem. + */ +static void inotify_dev_event_dequeue(struct inotify_device *dev) +{ + if (!list_empty(&dev->events)) { + struct inotify_kernel_event *kevent; + kevent = inotify_dev_get_event(dev); + remove_kevent(dev, kevent); + } +} + +/* + * inotify_dev_get_wd - returns the next WD for use by the given dev + * + * Callers must hold dev->sem. This function can sleep. + */ +static int inotify_dev_get_wd(struct inotify_device *dev, + struct inotify_watch *watch) +{ + int ret; + + do { + if (unlikely(!idr_pre_get(&dev->idr, GFP_KERNEL))) + return -ENOSPC; + ret = idr_get_new(&dev->idr, watch, &watch->wd); + } while (ret == -EAGAIN); + + return ret; +} + +/* + * find_inode - resolve a user-given path to a specific inode and return a nd + */ +static int find_inode(const char __user *dirname, struct nameidata *nd) +{ + int error; + + error = __user_walk(dirname, LOOKUP_FOLLOW, nd); + if (error) + return error; + /* you can only watch an inode if you have read permissions on it */ + error = permission(nd->dentry->d_inode, MAY_READ, NULL); + if (error) + path_release (nd); + return error; +} + +/* + * create_watch - creates a watch on the given device. + * + * Callers must hold dev->sem. Calls inotify_dev_get_wd() so may sleep. + * Both 'dev' and 'inode' (by way of nameidata) need to be pinned. + */ +static struct inotify_watch *create_watch(struct inotify_device *dev, + u32 mask, struct inode *inode) +{ + struct inotify_watch *watch; + int ret; + + if (atomic_read(&dev->user->inotify_watches) >= inotify_max_user_watches) + return ERR_PTR(-ENOSPC); + + watch = kmem_cache_alloc(watch_cachep, GFP_KERNEL); + if (unlikely(!watch)) + return ERR_PTR(-ENOMEM); + + ret = inotify_dev_get_wd(dev, watch); + if (unlikely(ret)) { + kmem_cache_free(watch_cachep, watch); + return ERR_PTR(ret); + } + + watch->mask = mask; + atomic_set(&watch->count, 0); + INIT_LIST_HEAD(&watch->d_list); + INIT_LIST_HEAD(&watch->i_list); + + /* save a reference to device and bump the count to make it official */ + get_inotify_dev(dev); + watch->dev = dev; + + /* + * 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); + + /* bump our own count, corresponding to our entry in dev->watches */ + get_inotify_watch(watch); + + atomic_inc(&dev->user->inotify_watches); + + return watch; +} + +/* + * inotify_find_dev - find the watch associated with the given inode and dev + * + * Callers must hold inode->inotify_sem. + */ +static struct inotify_watch *inode_find_dev(struct inode *inode, + struct inotify_device *dev) +{ + struct inotify_watch *watch; + + list_for_each_entry(watch, &inode->inotify_watches, i_list) { + if (watch->dev == dev) + return watch; + } + + return NULL; +} + +/* + * remove_watch_no_event - remove_watch() without the IN_IGNORED event. + */ +static void remove_watch_no_event(struct inotify_watch *watch, + struct inotify_device *dev) +{ + list_del(&watch->i_list); + list_del(&watch->d_list); + + atomic_dec(&dev->user->inotify_watches); + idr_remove(&dev->idr, watch->wd); + put_inotify_watch(watch); +} + +/* + * remove_watch - Remove a watch from both the device and the inode. Sends + * the IN_IGNORED event to the given device signifying that the inode is no + * longer watched. + * + * Callers must hold both inode->inotify_sem and dev->sem. We drop a + * reference to the inode before returning. + * + * The inode is not iput() so as to remain atomic. If the inode needs to be + * iput(), the call returns one. Otherwise, it returns zero. + */ +static void remove_watch(struct inotify_watch *watch,struct inotify_device *dev) +{ + inotify_dev_queue_event(dev, watch, IN_IGNORED, 0, NULL); + remove_watch_no_event(watch, dev); +} + +/* + * 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); +} + +/* Kernel API */ + +/** + * 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 + */ +void inotify_inode_queue_event(struct inode *inode, u32 mask, u32 cookie, + const char *name) +{ + struct inotify_watch *watch, *next; + + if (!inotify_inode_watched(inode)) + return; + + down(&inode->inotify_sem); + list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) { + u32 watch_mask = watch->mask; + if (watch_mask & mask) { + struct inotify_device *dev = watch->dev; + get_inotify_watch(watch); + down(&dev->sem); + inotify_dev_queue_event(dev, watch, mask, cookie, name); + if (watch_mask & IN_ONESHOT) + remove_watch_no_event(watch, dev); + up(&dev->sem); + put_inotify_watch(watch); + } + } + up(&inode->inotify_sem); +} +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; + + 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); + 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_sem 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 the remove_watch() 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_sem 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 */ + down(&inode->inotify_sem); + watches = &inode->inotify_watches; + list_for_each_entry_safe(watch, next_w, watches, i_list) { + struct inotify_device *dev = watch->dev; + down(&dev->sem); + inotify_dev_queue_event(dev, watch, IN_UNMOUNT,0,NULL); + remove_watch(watch, dev); + up(&dev->sem); + } + up(&inode->inotify_sem); + 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; + + down(&inode->inotify_sem); + list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) { + struct inotify_device *dev = watch->dev; + down(&dev->sem); + remove_watch(watch, dev); + up(&dev->sem); + } + up(&inode->inotify_sem); +} +EXPORT_SYMBOL_GPL(inotify_inode_is_dead); + +/* Device Interface */ + +static unsigned int inotify_poll(struct file *file, poll_table *wait) +{ + struct inotify_device *dev = file->private_data; + int ret = 0; + + poll_wait(file, &dev->wq, wait); + down(&dev->sem); + if (!list_empty(&dev->events)) + ret = POLLIN | POLLRDNORM; + up(&dev->sem); + + return ret; +} + +static ssize_t inotify_read(struct file *file, char __user *buf, + size_t count, loff_t *pos) +{ + size_t event_size = sizeof (struct inotify_event); + struct inotify_device *dev; + char __user *start; + int ret; + DEFINE_WAIT(wait); + + start = buf; + dev = file->private_data; + + while (1) { + int events; + + prepare_to_wait(&dev->wq, &wait, TASK_INTERRUPTIBLE); + + down(&dev->sem); + events = !list_empty(&dev->events); + up(&dev->sem); + if (events) { + ret = 0; + break; + } + + if (file->f_flags & O_NONBLOCK) { + ret = -EAGAIN; + break; + } + + if (signal_pending(current)) { + ret = -EINTR; + break; + } + + schedule(); + } + + finish_wait(&dev->wq, &wait); + if (ret) + return ret; + + down(&dev->sem); + while (1) { + struct inotify_kernel_event *kevent; + + ret = buf - start; + if (list_empty(&dev->events)) + break; + + kevent = inotify_dev_get_event(dev); + if (event_size + kevent->event.len > count) + break; + + if (copy_to_user(buf, &kevent->event, event_size)) { + ret = -EFAULT; + break; + } + buf += event_size; + count -= event_size; + + if (kevent->name) { + if (copy_to_user(buf, kevent->name, kevent->event.len)){ + ret = -EFAULT; + break; + } + buf += kevent->event.len; + count -= kevent->event.len; + } + + remove_kevent(dev, kevent); + } + up(&dev->sem); + + return ret; +} + +static int inotify_release(struct inode *ignored, struct file *file) +{ + struct inotify_device *dev = file->private_data; + + /* + * Destroy all of the watches on this device. 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_sem before dev->sem. The following works. + */ + while (1) { + struct inotify_watch *watch; + struct list_head *watches; + struct inode *inode; + + down(&dev->sem); + watches = &dev->watches; + if (list_empty(watches)) { + up(&dev->sem); + break; + } + watch = list_entry(watches->next, struct inotify_watch, d_list); + get_inotify_watch(watch); + up(&dev->sem); + + inode = watch->inode; + down(&inode->inotify_sem); + down(&dev->sem); + remove_watch_no_event(watch, dev); + up(&dev->sem); + up(&inode->inotify_sem); + put_inotify_watch(watch); + } + + /* destroy all of the events on this device */ + down(&dev->sem); + while (!list_empty(&dev->events)) + inotify_dev_event_dequeue(dev); + up(&dev->sem); + + /* free this device: the put matching the get in inotify_open() */ + put_inotify_dev(dev); + + return 0; +} + +/* + * inotify_ignore - handle the INOTIFY_IGNORE ioctl, asking that a given wd be + * removed from the device. + * + * Can sleep. + */ +static int inotify_ignore(struct inotify_device *dev, s32 wd) +{ + struct inotify_watch *watch; + struct inode *inode; + + down(&dev->sem); + watch = idr_find(&dev->idr, wd); + if (unlikely(!watch)) { + up(&dev->sem); + return -EINVAL; + } + get_inotify_watch(watch); + inode = watch->inode; + up(&dev->sem); + + down(&inode->inotify_sem); + down(&dev->sem); + + /* make sure that we did not race */ + watch = idr_find(&dev->idr, wd); + if (likely(watch)) + remove_watch(watch, dev); + + up(&dev->sem); + up(&inode->inotify_sem); + put_inotify_watch(watch); + + return 0; +} + +static long inotify_ioctl(struct file *file, unsigned int cmd, + unsigned long arg) +{ + struct inotify_device *dev; + void __user *p; + int ret = -ENOTTY; + + dev = file->private_data; + p = (void __user *) arg; + + switch (cmd) { + case FIONREAD: + ret = put_user(dev->queue_size, (int __user *) p); + break; + } + + return ret; +} + +static struct file_operations inotify_fops = { + .poll = inotify_poll, + .read = inotify_read, + .release = inotify_release, + .unlocked_ioctl = inotify_ioctl, + .compat_ioctl = inotify_ioctl, +}; + +asmlinkage long sys_inotify_init(void) +{ + struct inotify_device *dev; + struct user_struct *user; + int ret = -ENOTTY; + int fd; + struct file *filp; + + fd = get_unused_fd(); + if (fd < 0) { + ret = fd; + goto out; + } + + filp = get_empty_filp(); + if (!filp) { + put_unused_fd(fd); + ret = -ENFILE; + goto out; + } + filp->f_op = &inotify_fops; + filp->f_vfsmnt = mntget(inotify_mnt); + filp->f_dentry = dget(inotify_mnt->mnt_root); + filp->f_mapping = filp->f_dentry->d_inode->i_mapping; + filp->f_mode = FMODE_READ; + filp->f_flags = O_RDONLY; + + user = get_uid(current->user); + + if (unlikely(atomic_read(&user->inotify_devs) >= inotify_max_user_devices)) { + ret = -EMFILE; + goto out_err; + } + + dev = kmalloc(sizeof(struct inotify_device), GFP_KERNEL); + if (unlikely(!dev)) { + ret = -ENOMEM; + goto out_err; + } + + idr_init(&dev->idr); + INIT_LIST_HEAD(&dev->events); + INIT_LIST_HEAD(&dev->watches); + init_waitqueue_head(&dev->wq); + sema_init(&dev->sem, 1); + dev->event_count = 0; + dev->queue_size = 0; + dev->max_events = inotify_max_queued_events; + dev->user = user; + atomic_set(&dev->count, 0); + + get_inotify_dev(dev); + atomic_inc(&user->inotify_devs); + + filp->private_data = dev; + fd_install (fd, filp); + return fd; +out_err: + put_unused_fd (fd); + put_filp (filp); + free_uid(user); +out: + return ret; +} + +asmlinkage long sys_inotify_add_watch(int fd, const char *path, u32 mask) +{ + struct inotify_watch *watch, *old; + struct inode *inode; + struct inotify_device *dev; + struct nameidata nd; + struct file *filp; + int ret; + + filp = fget(fd); + if (!filp) + return -EBADF; + + dev = filp->private_data; + + ret = find_inode ((const char __user*)path, &nd); + if (ret) + goto fput_and_out; + + /* Held in place by reference in nd */ + inode = nd.dentry->d_inode; + + down(&inode->inotify_sem); + down(&dev->sem); + + /* don't let user-space set invalid bits: we don't want flags set */ + mask &= IN_ALL_EVENTS; + if (!mask) { + ret = -EINVAL; + goto out; + } + + /* + * Handle the case of re-adding a watch on an (inode,dev) pair that we + * are already watching. We just update the mask and return its wd. + */ + old = inode_find_dev(inode, dev); + if (unlikely(old)) { + old->mask = mask; + ret = old->wd; + goto out; + } + + watch = create_watch(dev, mask, inode); + if (unlikely(IS_ERR(watch))) { + ret = PTR_ERR(watch); + goto out; + } + + /* Add the watch to the device's and the inode's list */ + list_add(&watch->d_list, &dev->watches); + list_add(&watch->i_list, &inode->inotify_watches); + ret = watch->wd; +out: + path_release (&nd); + up(&dev->sem); + up(&inode->inotify_sem); +fput_and_out: + fput(filp); + return ret; +} + +asmlinkage long sys_inotify_rm_watch(int fd, u32 wd) +{ + struct file *filp; + struct inotify_device *dev; + int ret; + + filp = fget(fd); + if (!filp) + return -EBADF; + dev = filp->private_data; + ret = inotify_ignore (dev, wd); + fput(filp); + return ret; +} + +static struct super_block * +inotify_get_sb(struct file_system_type *fs_type, int flags, + const char *dev_name, void *data) +{ + return get_sb_pseudo(fs_type, "inotify", NULL, 0xBAD1DEA); +} + +static struct file_system_type inotify_fs_type = { + .name = "inotifyfs", + .get_sb = inotify_get_sb, + .kill_sb = kill_anon_super, +}; + +/* + * inotify_init - Our initialization function. Note that we cannnot return + * error because we have compiled-in VFS hooks. So an (unlikely) failure here + * must result in panic(). + */ +static int __init inotify_init(void) +{ + register_filesystem(&inotify_fs_type); + inotify_mnt = kern_mount(&inotify_fs_type); + + inotify_max_queued_events = 8192; + inotify_max_user_devices = 128; + inotify_max_user_watches = 8192; + + atomic_set(&inotify_cookie, 0); + + watch_cachep = kmem_cache_create("inotify_watch_cache", + sizeof(struct inotify_watch), + 0, SLAB_PANIC, NULL, NULL); + event_cachep = kmem_cache_create("inotify_event_cache", + sizeof(struct inotify_kernel_event), + 0, SLAB_PANIC, NULL, NULL); + + printk(KERN_INFO "inotify syscall\n"); + + return 0; +} + +module_init(inotify_init); |
