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TOMOYO Linux Cross Reference
Linux/fs/notify/inode_mark.c

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  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 <asm/atomic.h>
 27 
 28 #include <linux/fsnotify_backend.h>
 29 #include "fsnotify.h"
 30 
 31 #include "../internal.h"
 32 
 33 /*
 34  * Recalculate the mask of events relevant to a given inode locked.
 35  */
 36 static void fsnotify_recalc_inode_mask_locked(struct inode *inode)
 37 {
 38         struct fsnotify_mark *mark;
 39         struct hlist_node *pos;
 40         __u32 new_mask = 0;
 41 
 42         assert_spin_locked(&inode->i_lock);
 43 
 44         hlist_for_each_entry(mark, pos, &inode->i_fsnotify_marks, i.i_list)
 45                 new_mask |= mark->mask;
 46         inode->i_fsnotify_mask = new_mask;
 47 }
 48 
 49 /*
 50  * Recalculate the inode->i_fsnotify_mask, or the mask of all FS_* event types
 51  * any notifier is interested in hearing for this inode.
 52  */
 53 void fsnotify_recalc_inode_mask(struct inode *inode)
 54 {
 55         spin_lock(&inode->i_lock);
 56         fsnotify_recalc_inode_mask_locked(inode);
 57         spin_unlock(&inode->i_lock);
 58 
 59         __fsnotify_update_child_dentry_flags(inode);
 60 }
 61 
 62 void fsnotify_destroy_inode_mark(struct fsnotify_mark *mark)
 63 {
 64         struct inode *inode = mark->i.inode;
 65 
 66         assert_spin_locked(&mark->lock);
 67         assert_spin_locked(&mark->group->mark_lock);
 68 
 69         spin_lock(&inode->i_lock);
 70 
 71         hlist_del_init_rcu(&mark->i.i_list);
 72         mark->i.inode = NULL;
 73 
 74         /*
 75          * this mark is now off the inode->i_fsnotify_marks list and we
 76          * hold the inode->i_lock, so this is the perfect time to update the
 77          * inode->i_fsnotify_mask
 78          */
 79         fsnotify_recalc_inode_mask_locked(inode);
 80 
 81         spin_unlock(&inode->i_lock);
 82 }
 83 
 84 /*
 85  * Given an inode, destroy all of the marks associated with that inode.
 86  */
 87 void fsnotify_clear_marks_by_inode(struct inode *inode)
 88 {
 89         struct fsnotify_mark *mark, *lmark;
 90         struct hlist_node *pos, *n;
 91         LIST_HEAD(free_list);
 92 
 93         spin_lock(&inode->i_lock);
 94         hlist_for_each_entry_safe(mark, pos, n, &inode->i_fsnotify_marks, i.i_list) {
 95                 list_add(&mark->i.free_i_list, &free_list);
 96                 hlist_del_init_rcu(&mark->i.i_list);
 97                 fsnotify_get_mark(mark);
 98         }
 99         spin_unlock(&inode->i_lock);
100 
101         list_for_each_entry_safe(mark, lmark, &free_list, i.free_i_list) {
102                 fsnotify_destroy_mark(mark);
103                 fsnotify_put_mark(mark);
104         }
105 }
106 
107 /*
108  * Given a group clear all of the inode marks associated with that group.
109  */
110 void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
111 {
112         fsnotify_clear_marks_by_group_flags(group, FSNOTIFY_MARK_FLAG_INODE);
113 }
114 
115 /*
116  * given a group and inode, find the mark associated with that combination.
117  * if found take a reference to that mark and return it, else return NULL
118  */
119 struct fsnotify_mark *fsnotify_find_inode_mark_locked(struct fsnotify_group *group,
120                                                       struct inode *inode)
121 {
122         struct fsnotify_mark *mark;
123         struct hlist_node *pos;
124 
125         assert_spin_locked(&inode->i_lock);
126 
127         hlist_for_each_entry(mark, pos, &inode->i_fsnotify_marks, i.i_list) {
128                 if (mark->group == group) {
129                         fsnotify_get_mark(mark);
130                         return mark;
131                 }
132         }
133         return NULL;
134 }
135 
136 /*
137  * given a group and inode, find the mark associated with that combination.
138  * if found take a reference to that mark and return it, else return NULL
139  */
140 struct fsnotify_mark *fsnotify_find_inode_mark(struct fsnotify_group *group,
141                                                struct inode *inode)
142 {
143         struct fsnotify_mark *mark;
144 
145         spin_lock(&inode->i_lock);
146         mark = fsnotify_find_inode_mark_locked(group, inode);
147         spin_unlock(&inode->i_lock);
148 
149         return mark;
150 }
151 
152 /*
153  * If we are setting a mark mask on an inode mark we should pin the inode
154  * in memory.
155  */
156 void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *mark,
157                                          __u32 mask)
158 {
159         struct inode *inode;
160 
161         assert_spin_locked(&mark->lock);
162 
163         if (mask &&
164             mark->i.inode &&
165             !(mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED)) {
166                 mark->flags |= FSNOTIFY_MARK_FLAG_OBJECT_PINNED;
167                 inode = igrab(mark->i.inode);
168                 /*
169                  * we shouldn't be able to get here if the inode wasn't
170                  * already safely held in memory.  But bug in case it
171                  * ever is wrong.
172                  */
173                 BUG_ON(!inode);
174         }
175 }
176 
177 /*
178  * Attach an initialized mark to a given inode.
179  * These marks may be used for the fsnotify backend to determine which
180  * event types should be delivered to which group and for which inodes.  These
181  * marks are ordered according to priority, highest number first, and then by
182  * the group's location in memory.
183  */
184 int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
185                             struct fsnotify_group *group, struct inode *inode,
186                             int allow_dups)
187 {
188         struct fsnotify_mark *lmark;
189         struct hlist_node *node, *last = NULL;
190         int ret = 0;
191 
192         mark->flags |= FSNOTIFY_MARK_FLAG_INODE;
193 
194         assert_spin_locked(&mark->lock);
195         assert_spin_locked(&group->mark_lock);
196 
197         spin_lock(&inode->i_lock);
198 
199         mark->i.inode = inode;
200 
201         /* is mark the first mark? */
202         if (hlist_empty(&inode->i_fsnotify_marks)) {
203                 hlist_add_head_rcu(&mark->i.i_list, &inode->i_fsnotify_marks);
204                 goto out;
205         }
206 
207         /* should mark be in the middle of the current list? */
208         hlist_for_each_entry(lmark, node, &inode->i_fsnotify_marks, i.i_list) {
209                 last = node;
210 
211                 if ((lmark->group == group) && !allow_dups) {
212                         ret = -EEXIST;
213                         goto out;
214                 }
215 
216                 if (mark->group->priority < lmark->group->priority)
217                         continue;
218 
219                 if ((mark->group->priority == lmark->group->priority) &&
220                     (mark->group < lmark->group))
221                         continue;
222 
223                 hlist_add_before_rcu(&mark->i.i_list, &lmark->i.i_list);
224                 goto out;
225         }
226 
227         BUG_ON(last == NULL);
228         /* mark should be the last entry.  last is the current last entry */
229         hlist_add_after_rcu(last, &mark->i.i_list);
230 out:
231         fsnotify_recalc_inode_mask_locked(inode);
232         spin_unlock(&inode->i_lock);
233 
234         return ret;
235 }
236 
237 /**
238  * fsnotify_unmount_inodes - an sb is unmounting.  handle any watched inodes.
239  * @list: list of inodes being unmounted (sb->s_inodes)
240  *
241  * Called during unmount with no locks held, so needs to be safe against
242  * concurrent modifiers. We temporarily drop inode_sb_list_lock and CAN block.
243  */
244 void fsnotify_unmount_inodes(struct list_head *list)
245 {
246         struct inode *inode, *next_i, *need_iput = NULL;
247 
248         spin_lock(&inode_sb_list_lock);
249         list_for_each_entry_safe(inode, next_i, list, i_sb_list) {
250                 struct inode *need_iput_tmp;
251 
252                 /*
253                  * We cannot __iget() an inode in state I_FREEING,
254                  * I_WILL_FREE, or I_NEW which is fine because by that point
255                  * the inode cannot have any associated watches.
256                  */
257                 spin_lock(&inode->i_lock);
258                 if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
259                         spin_unlock(&inode->i_lock);
260                         continue;
261                 }
262 
263                 /*
264                  * If i_count is zero, the inode cannot have any watches and
265                  * doing an __iget/iput with MS_ACTIVE clear would actually
266                  * evict all inodes with zero i_count from icache which is
267                  * unnecessarily violent and may in fact be illegal to do.
268                  */
269                 if (!atomic_read(&inode->i_count)) {
270                         spin_unlock(&inode->i_lock);
271                         continue;
272                 }
273 
274                 need_iput_tmp = need_iput;
275                 need_iput = NULL;
276 
277                 /* In case fsnotify_inode_delete() drops a reference. */
278                 if (inode != need_iput_tmp)
279                         __iget(inode);
280                 else
281                         need_iput_tmp = NULL;
282                 spin_unlock(&inode->i_lock);
283 
284                 /* In case the dropping of a reference would nuke next_i. */
285                 if ((&next_i->i_sb_list != list) &&
286                     atomic_read(&next_i->i_count)) {
287                         spin_lock(&next_i->i_lock);
288                         if (!(next_i->i_state & (I_FREEING | I_WILL_FREE))) {
289                                 __iget(next_i);
290                                 need_iput = next_i;
291                         }
292                         spin_unlock(&next_i->i_lock);
293                 }
294 
295                 /*
296                  * We can safely drop inode_sb_list_lock here because we hold
297                  * references on both inode and next_i.  Also no new inodes
298                  * will be added since the umount has begun.
299                  */
300                 spin_unlock(&inode_sb_list_lock);
301 
302                 if (need_iput_tmp)
303                         iput(need_iput_tmp);
304 
305                 /* for each watch, send FS_UNMOUNT and then remove it */
306                 fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
307 
308                 fsnotify_inode_delete(inode);
309 
310                 iput(inode);
311 
312                 spin_lock(&inode_sb_list_lock);
313         }
314         spin_unlock(&inode_sb_list_lock);
315 }
316 

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