1/*
  2 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
  3 *
  4 *  This program is free software; you can redistribute it and/or modify
  5 *  it under the terms of the GNU General Public License as published by
  6 *  the Free Software Foundation; either version 2, or (at your option)
  7 *  any later version.
  8 *
  9 *  This program is distributed in the hope that it will be useful,
 10 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 *  GNU General Public License for more details.
 13 *
 14 *  You should have received a copy of the GNU General Public License
 15 *  along with this program; see the file COPYING.  If not, write to
 16 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
 17 */
 18
 19#include <linux/fs.h>
 20#include <linux/init.h>
 21#include <linux/kernel.h>
 22#include <linux/module.h>
 23#include <linux/mutex.h>
 24#include <linux/spinlock.h>
 25
 26#include <linux/atomic.h>
 27
 28#include <linux/fsnotify_backend.h>
 29#include "fsnotify.h"
 30
 31#include "../internal.h"
 32
 33/*
 34 * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
 35 * any notifier is interested in hearing for this inode.
 36 */
 37void fsnotify_recalc_inode_mask(struct inode *inode)
 38{
 39	spin_lock(&inode->i_lock);
 40	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
 41	spin_unlock(&inode->i_lock);
 42
 43	__fsnotify_update_child_dentry_flags(inode);
 44}
 45
 46void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
 47{
 48	struct inode *inode = mark->inode;
 49
 50	BUG_ON(!mutex_is_locked(&mark->group->mark_mutex));
 51	assert_spin_locked(&mark->lock);
 52
 53	spin_lock(&inode->i_lock);
 54
 55	hlist_del_init_rcu(&mark->obj_list);
 56	mark->inode = NULL;
 57
 58	/*
 59	 * this mark is now off the inode->i_fsnotify_marks list and we
 60	 * hold the inode->i_lock, so this is the perfect time to update the
 61	 * inode->i_fsnotify_mask
 62	 */
 63	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
 64	spin_unlock(&inode->i_lock);
 65}
 66
 67/*
 68 * Given a group clear all of the inode marks associated with that group.
 69 */
 70void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
 71{
 72	fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
 73}
 74
 75/*
 76 * given a group and inode, find the mark associated with that combination.
 77 * if found take a reference to that mark and return it, else return NULL
 78 */
 79struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
 80					       struct inode *inode)
 81{
 82	struct fsnotify_mark *mark;
 83
 84	spin_lock(&inode->i_lock);
 85	mark = fsnotify_find_mark(&inode->i_fsnotify_marks, group);
 86	spin_unlock(&inode->i_lock);
 87
 88	return mark;
 89}
 90
 91/*
 92 * If we are setting a mark mask on an inode mark we should pin the inode
 93 * in memory.
 94 */
 95void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
 96					 __u32 mask)
 97{
 98	struct inode *inode;
 99
100	assert_spin_locked(&mark->lock);
101
102	if (mask &&
103	    mark->inode &&
104	    !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
105		mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
106		inode = igrab(mark->inode);
107		/*
108		 * we shouldn't be able to get here if the inode wasn't
109		 * already safely held in memory.  But bug in case it
110		 * ever is wrong.
111		 */
112		BUG_ON(!inode);
113	}
114}
115
116/*
117 * Attach an initialized mark to a given inode.
118 * These marks may be used for the fsnotify backend to determine which
119 * event types should be delivered to which group and for which inodes.  These
120 * marks are ordered according to priority, highest number first, and then by
121 * the group's location in memory.
122 */
123int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
124			    struct fsnotify_group *group, struct inode *inode,
125			    int allow_dups)
126{
127	int ret;
128
129	mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
130
131	BUG_ON(!mutex_is_locked(&group->mark_mutex));
132	assert_spin_locked(&mark->lock);
133
134	spin_lock(&inode->i_lock);
135	mark->inode = inode;
136	ret = fsnotify_add_mark_list(&inode->i_fsnotify_marks, mark,
137				     allow_dups);
138	inode->i_fsnotify_mask = fsnotify_recalc_mask(&inode->i_fsnotify_marks);
139	spin_unlock(&inode->i_lock);
140
141	return ret;
142}
143
144/**
145 * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
146 * @sb: superblock being unmounted.
147 *
148 * Called during unmount with no locks held, so needs to be safe against
149 * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
150 */
151void fsnotify_unmount_inodes(struct super_block *sb)
152{
153	struct inode *inode, *next_i, *need_iput = NULL;
154
155	spin_lock(&sb->s_inode_list_lock);
156	list_for_each_entry_safe(inode, next_i, &sb->s_inodes, i_sb_list) {
157		struct inode *need_iput_tmp;
158
159		/*
160		 * We cannot __iget() an inode in state I_FREEING,
161		 * I_WILL_FREE, or I_NEW which is fine because by that point
162		 * the inode cannot have any associated watches.
163		 */
164		spin_lock(&inode->i_lock);
165		if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
166			spin_unlock(&inode->i_lock);
167			continue;
168		}
169
170		/*
171		 * If i_count is zero, the inode cannot have any watches and
172		 * doing an __iget/iput with MS_ACTIVE clear would actually
173		 * evict all inodes with zero i_count from icache which is
174		 * unnecessarily violent and may in fact be illegal to do.
175		 */
176		if (!atomic_read(&inode->i_count)) {
177			spin_unlock(&inode->i_lock);
178			continue;
179		}
180
181		need_iput_tmp = need_iput;
182		need_iput = NULL;
183
184		/* In case fsnotify_inode_delete() drops a reference. */
185		if (inode != need_iput_tmp)
186			__iget(inode);
187		else
188			need_iput_tmp = NULL;
189		spin_unlock(&inode->i_lock);
190
191		/* In case the dropping of a reference would nuke next_i. */
192		while (&next_i->i_sb_list != &sb->s_inodes) {
193			spin_lock(&next_i->i_lock);
194			if (!(next_i->i_state & (I_FREEING | I_WILL_FREE)) &&
195						atomic_read(&next_i->i_count)) {
196				__iget(next_i);
197				need_iput = next_i;
198				spin_unlock(&next_i->i_lock);
199				break;
200			}
201			spin_unlock(&next_i->i_lock);
202			next_i = list_next_entry(next_i, i_sb_list);
203		}
204
205		/*
206		 * We can safely drop s_inode_list_lock here because either
207		 * we actually hold references on both inode and next_i or
208		 * end of list.  Also no new inodes will be added since the
209		 * umount has begun.
210		 */
211		spin_unlock(&sb->s_inode_list_lock);
212
213		if (need_iput_tmp)
214			iput(need_iput_tmp);
215
216		/* for each watch, send FS_UNMOUNT and then remove it */
217		fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
218
219		fsnotify_inode_delete(inode);
220
221		iput(inode);
222
223		spin_lock(&sb->s_inode_list_lock);
224	}
225	spin_unlock(&sb->s_inode_list_lock);
226}