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![Amy Griffis](/assets/img/avatar_default.png)
Allow callers to remove watches from their event handler via inotify_remove_watch_locked(). This functionality can be used to achieve IN_ONESHOT-like functionality for a subset of events in the mask. Signed-off-by: Amy Griffis <amy.griffis@hp.com> Acked-by: Robert Love <rml@novell.com> Acked-by: John McCutchan <john@johnmccutchan.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
729 lines
19 KiB
C
729 lines
19 KiB
C
/*
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* fs/inotify.c - inode-based file event notifications
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*
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* Authors:
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* John McCutchan <ttb@tentacle.dhs.org>
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* Robert Love <rml@novell.com>
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*
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* Kernel API added by: Amy Griffis <amy.griffis@hp.com>
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*
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* Copyright (C) 2005 John McCutchan
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* Copyright 2006 Hewlett-Packard Development Company, L.P.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2, or (at your option) any
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* later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/spinlock.h>
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#include <linux/idr.h>
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#include <linux/slab.h>
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <linux/writeback.h>
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#include <linux/inotify.h>
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static atomic_t inotify_cookie;
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/*
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* Lock ordering:
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*
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* dentry->d_lock (used to keep d_move() away from dentry->d_parent)
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* iprune_mutex (synchronize shrink_icache_memory())
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* inode_lock (protects the super_block->s_inodes list)
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* inode->inotify_mutex (protects inode->inotify_watches and watches->i_list)
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* inotify_handle->mutex (protects inotify_handle and watches->h_list)
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*
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* The inode->inotify_mutex and inotify_handle->mutex and held during execution
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* of a caller's event handler. Thus, the caller must not hold any locks
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* taken in their event handler while calling any of the published inotify
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* interfaces.
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*/
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/*
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* Lifetimes of the three main data structures--inotify_handle, inode, and
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* inotify_watch--are managed by reference count.
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*
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* inotify_handle: Lifetime is from inotify_init() to inotify_destroy().
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* Additional references can bump the count via get_inotify_handle() and drop
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* the count via put_inotify_handle().
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*
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* inotify_watch: for inotify's purposes, lifetime is from inotify_add_watch()
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* to remove_watch_no_event(). Additional references can bump the count via
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* get_inotify_watch() and drop the count via put_inotify_watch(). The caller
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* is reponsible for the final put after receiving IN_IGNORED, or when using
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* IN_ONESHOT after receiving the first event. Inotify does the final put if
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* inotify_destroy() is called.
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*
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* inode: Pinned so long as the inode is associated with a watch, from
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* inotify_add_watch() to the final put_inotify_watch().
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*/
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/*
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* struct inotify_handle - represents an inotify instance
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*
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* This structure is protected by the mutex 'mutex'.
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*/
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struct inotify_handle {
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struct idr idr; /* idr mapping wd -> watch */
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struct mutex mutex; /* protects this bad boy */
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struct list_head watches; /* list of watches */
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atomic_t count; /* reference count */
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u32 last_wd; /* the last wd allocated */
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const struct inotify_operations *in_ops; /* inotify caller operations */
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};
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static inline void get_inotify_handle(struct inotify_handle *ih)
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{
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atomic_inc(&ih->count);
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}
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static inline void put_inotify_handle(struct inotify_handle *ih)
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{
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if (atomic_dec_and_test(&ih->count)) {
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idr_destroy(&ih->idr);
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kfree(ih);
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}
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}
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/**
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* get_inotify_watch - grab a reference to an inotify_watch
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* @watch: watch to grab
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*/
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void get_inotify_watch(struct inotify_watch *watch)
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{
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atomic_inc(&watch->count);
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}
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EXPORT_SYMBOL_GPL(get_inotify_watch);
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/**
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* put_inotify_watch - decrements the ref count on a given watch. cleans up
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* watch references if the count reaches zero. inotify_watch is freed by
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* inotify callers via the destroy_watch() op.
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* @watch: watch to release
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*/
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void put_inotify_watch(struct inotify_watch *watch)
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{
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if (atomic_dec_and_test(&watch->count)) {
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struct inotify_handle *ih = watch->ih;
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iput(watch->inode);
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ih->in_ops->destroy_watch(watch);
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put_inotify_handle(ih);
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}
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}
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EXPORT_SYMBOL_GPL(put_inotify_watch);
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/*
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* inotify_handle_get_wd - returns the next WD for use by the given handle
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*
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* Callers must hold ih->mutex. This function can sleep.
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*/
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static int inotify_handle_get_wd(struct inotify_handle *ih,
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struct inotify_watch *watch)
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{
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int ret;
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do {
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if (unlikely(!idr_pre_get(&ih->idr, GFP_KERNEL)))
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return -ENOSPC;
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ret = idr_get_new_above(&ih->idr, watch, ih->last_wd+1, &watch->wd);
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} while (ret == -EAGAIN);
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if (likely(!ret))
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ih->last_wd = watch->wd;
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return ret;
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}
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/*
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* inotify_inode_watched - returns nonzero if there are watches on this inode
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* and zero otherwise. We call this lockless, we do not care if we race.
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*/
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static inline int inotify_inode_watched(struct inode *inode)
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{
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return !list_empty(&inode->inotify_watches);
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}
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/*
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* Get child dentry flag into synch with parent inode.
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* Flag should always be clear for negative dentrys.
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*/
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static void set_dentry_child_flags(struct inode *inode, int watched)
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{
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struct dentry *alias;
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spin_lock(&dcache_lock);
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list_for_each_entry(alias, &inode->i_dentry, d_alias) {
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struct dentry *child;
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list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
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if (!child->d_inode) {
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WARN_ON(child->d_flags & DCACHE_INOTIFY_PARENT_WATCHED);
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continue;
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}
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spin_lock(&child->d_lock);
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if (watched) {
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WARN_ON(child->d_flags &
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DCACHE_INOTIFY_PARENT_WATCHED);
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child->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
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} else {
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WARN_ON(!(child->d_flags &
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DCACHE_INOTIFY_PARENT_WATCHED));
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child->d_flags&=~DCACHE_INOTIFY_PARENT_WATCHED;
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}
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spin_unlock(&child->d_lock);
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}
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}
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spin_unlock(&dcache_lock);
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}
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/*
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* inotify_find_handle - find the watch associated with the given inode and
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* handle
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*
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* Callers must hold inode->inotify_mutex.
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*/
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static struct inotify_watch *inode_find_handle(struct inode *inode,
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struct inotify_handle *ih)
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{
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struct inotify_watch *watch;
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list_for_each_entry(watch, &inode->inotify_watches, i_list) {
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if (watch->ih == ih)
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return watch;
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}
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return NULL;
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}
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/*
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* remove_watch_no_event - remove watch without the IN_IGNORED event.
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*
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* Callers must hold both inode->inotify_mutex and ih->mutex.
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*/
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static void remove_watch_no_event(struct inotify_watch *watch,
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struct inotify_handle *ih)
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{
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list_del(&watch->i_list);
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list_del(&watch->h_list);
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if (!inotify_inode_watched(watch->inode))
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set_dentry_child_flags(watch->inode, 0);
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idr_remove(&ih->idr, watch->wd);
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}
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/**
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* inotify_remove_watch_locked - Remove a watch from both the handle and the
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* inode. Sends the IN_IGNORED event signifying that the inode is no longer
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* watched. May be invoked from a caller's event handler.
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* @ih: inotify handle associated with watch
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* @watch: watch to remove
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*
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* Callers must hold both inode->inotify_mutex and ih->mutex.
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*/
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void inotify_remove_watch_locked(struct inotify_handle *ih,
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struct inotify_watch *watch)
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{
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remove_watch_no_event(watch, ih);
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ih->in_ops->handle_event(watch, watch->wd, IN_IGNORED, 0, NULL, NULL);
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}
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EXPORT_SYMBOL_GPL(inotify_remove_watch_locked);
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/* Kernel API for producing events */
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/*
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* inotify_d_instantiate - instantiate dcache entry for inode
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*/
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void inotify_d_instantiate(struct dentry *entry, struct inode *inode)
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{
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struct dentry *parent;
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if (!inode)
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return;
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WARN_ON(entry->d_flags & DCACHE_INOTIFY_PARENT_WATCHED);
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spin_lock(&entry->d_lock);
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parent = entry->d_parent;
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if (parent->d_inode && inotify_inode_watched(parent->d_inode))
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entry->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
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spin_unlock(&entry->d_lock);
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}
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/*
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* inotify_d_move - dcache entry has been moved
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*/
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void inotify_d_move(struct dentry *entry)
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{
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struct dentry *parent;
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parent = entry->d_parent;
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if (inotify_inode_watched(parent->d_inode))
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entry->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
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else
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entry->d_flags &= ~DCACHE_INOTIFY_PARENT_WATCHED;
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}
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/**
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* inotify_inode_queue_event - queue an event to all watches on this inode
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* @inode: inode event is originating from
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* @mask: event mask describing this event
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* @cookie: cookie for synchronization, or zero
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* @name: filename, if any
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* @n_inode: inode associated with name
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*/
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void inotify_inode_queue_event(struct inode *inode, u32 mask, u32 cookie,
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const char *name, struct inode *n_inode)
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{
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struct inotify_watch *watch, *next;
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if (!inotify_inode_watched(inode))
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return;
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mutex_lock(&inode->inotify_mutex);
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list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
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u32 watch_mask = watch->mask;
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if (watch_mask & mask) {
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struct inotify_handle *ih= watch->ih;
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mutex_lock(&ih->mutex);
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if (watch_mask & IN_ONESHOT)
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remove_watch_no_event(watch, ih);
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ih->in_ops->handle_event(watch, watch->wd, mask, cookie,
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name, n_inode);
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mutex_unlock(&ih->mutex);
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}
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}
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mutex_unlock(&inode->inotify_mutex);
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}
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EXPORT_SYMBOL_GPL(inotify_inode_queue_event);
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/**
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* inotify_dentry_parent_queue_event - queue an event to a dentry's parent
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* @dentry: the dentry in question, we queue against this dentry's parent
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* @mask: event mask describing this event
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* @cookie: cookie for synchronization, or zero
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* @name: filename, if any
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*/
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void inotify_dentry_parent_queue_event(struct dentry *dentry, u32 mask,
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u32 cookie, const char *name)
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{
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struct dentry *parent;
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struct inode *inode;
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if (!(dentry->d_flags & DCACHE_INOTIFY_PARENT_WATCHED))
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return;
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spin_lock(&dentry->d_lock);
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parent = dentry->d_parent;
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inode = parent->d_inode;
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if (inotify_inode_watched(inode)) {
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dget(parent);
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spin_unlock(&dentry->d_lock);
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inotify_inode_queue_event(inode, mask, cookie, name,
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dentry->d_inode);
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dput(parent);
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} else
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spin_unlock(&dentry->d_lock);
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}
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EXPORT_SYMBOL_GPL(inotify_dentry_parent_queue_event);
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/**
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* inotify_get_cookie - return a unique cookie for use in synchronizing events.
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*/
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u32 inotify_get_cookie(void)
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{
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return atomic_inc_return(&inotify_cookie);
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}
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EXPORT_SYMBOL_GPL(inotify_get_cookie);
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/**
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* inotify_unmount_inodes - an sb is unmounting. handle any watched inodes.
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* @list: list of inodes being unmounted (sb->s_inodes)
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*
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* Called with inode_lock held, protecting the unmounting super block's list
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* of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay.
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* We temporarily drop inode_lock, however, and CAN block.
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*/
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void inotify_unmount_inodes(struct list_head *list)
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{
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struct inode *inode, *next_i, *need_iput = NULL;
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list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
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struct inotify_watch *watch, *next_w;
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struct inode *need_iput_tmp;
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struct list_head *watches;
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/*
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* If i_count is zero, the inode cannot have any watches and
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* doing an __iget/iput with MS_ACTIVE clear would actually
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* evict all inodes with zero i_count from icache which is
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* unnecessarily violent and may in fact be illegal to do.
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*/
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if (!atomic_read(&inode->i_count))
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continue;
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/*
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* We cannot __iget() an inode in state I_CLEAR, I_FREEING, or
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* I_WILL_FREE which is fine because by that point the inode
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* cannot have any associated watches.
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*/
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if (inode->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))
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continue;
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need_iput_tmp = need_iput;
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need_iput = NULL;
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/* In case inotify_remove_watch_locked() drops a reference. */
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if (inode != need_iput_tmp)
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__iget(inode);
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else
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need_iput_tmp = NULL;
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/* In case the dropping of a reference would nuke next_i. */
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if ((&next_i->i_sb_list != list) &&
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atomic_read(&next_i->i_count) &&
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!(next_i->i_state & (I_CLEAR | I_FREEING |
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I_WILL_FREE))) {
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__iget(next_i);
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need_iput = next_i;
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}
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/*
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* We can safely drop inode_lock here because we hold
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* references on both inode and next_i. Also no new inodes
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* will be added since the umount has begun. Finally,
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* iprune_mutex keeps shrink_icache_memory() away.
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*/
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spin_unlock(&inode_lock);
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if (need_iput_tmp)
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iput(need_iput_tmp);
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/* for each watch, send IN_UNMOUNT and then remove it */
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mutex_lock(&inode->inotify_mutex);
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watches = &inode->inotify_watches;
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list_for_each_entry_safe(watch, next_w, watches, i_list) {
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struct inotify_handle *ih= watch->ih;
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mutex_lock(&ih->mutex);
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ih->in_ops->handle_event(watch, watch->wd, IN_UNMOUNT, 0,
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NULL, NULL);
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inotify_remove_watch_locked(ih, watch);
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mutex_unlock(&ih->mutex);
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}
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mutex_unlock(&inode->inotify_mutex);
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iput(inode);
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spin_lock(&inode_lock);
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}
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}
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EXPORT_SYMBOL_GPL(inotify_unmount_inodes);
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/**
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* inotify_inode_is_dead - an inode has been deleted, cleanup any watches
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* @inode: inode that is about to be removed
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*/
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void inotify_inode_is_dead(struct inode *inode)
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{
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struct inotify_watch *watch, *next;
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mutex_lock(&inode->inotify_mutex);
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list_for_each_entry_safe(watch, next, &inode->inotify_watches, i_list) {
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struct inotify_handle *ih = watch->ih;
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mutex_lock(&ih->mutex);
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inotify_remove_watch_locked(ih, watch);
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mutex_unlock(&ih->mutex);
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}
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mutex_unlock(&inode->inotify_mutex);
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}
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EXPORT_SYMBOL_GPL(inotify_inode_is_dead);
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/* Kernel Consumer API */
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/**
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* inotify_init - allocate and initialize an inotify instance
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* @ops: caller's inotify operations
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*/
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struct inotify_handle *inotify_init(const struct inotify_operations *ops)
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{
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struct inotify_handle *ih;
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ih = kmalloc(sizeof(struct inotify_handle), GFP_KERNEL);
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if (unlikely(!ih))
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return ERR_PTR(-ENOMEM);
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idr_init(&ih->idr);
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INIT_LIST_HEAD(&ih->watches);
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mutex_init(&ih->mutex);
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ih->last_wd = 0;
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ih->in_ops = ops;
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atomic_set(&ih->count, 0);
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get_inotify_handle(ih);
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return ih;
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}
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EXPORT_SYMBOL_GPL(inotify_init);
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/**
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* inotify_init_watch - initialize an inotify watch
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* @watch: watch to initialize
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*/
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void inotify_init_watch(struct inotify_watch *watch)
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{
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INIT_LIST_HEAD(&watch->h_list);
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INIT_LIST_HEAD(&watch->i_list);
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atomic_set(&watch->count, 0);
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get_inotify_watch(watch); /* initial get */
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|
}
|
|
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_entry(watches->next, 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_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);
|