/* * fs/inotify.c - inode-based file event notifications * * Authors: * John McCutchan * Robert Love * * Kernel API added by: Amy Griffis * * 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 #include #include #include #include #include #include #include #include #include #include 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) 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; 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; 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 inode *inode; mutex_lock(&ih->mutex); watch = idr_find(&ih->idr, wd); if (unlikely(!watch)) { mutex_unlock(&ih->mutex); return -EINVAL; } get_inotify_watch(watch); inode = watch->inode; mutex_unlock(&ih->mutex); 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); put_inotify_watch(watch); 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);