fs/notify/fsnotify.c

   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/dcache.h>
  20 #include <linux/fs.h>
  21 #include <linux/init.h>
  22 #include <linux/module.h>
  23 #include <linux/srcu.h>
  24
  25 #include <linux/fsnotify_backend.h>
  26 #include "fsnotify.h"
  27
  28 /*
  29  * Clear all of the marks on an inode when it is being evicted from core
  30  */
  31 void __fsnotify_inode_delete(struct inode *inode)
  32 {
  33         fsnotify_clear_marks_by_inode(inode);
  34 }
  35 EXPORT_SYMBOL_GPL(__fsnotify_inode_delete);
  36
  37 /*
  38  * This is the main call to fsnotify.  The VFS calls into hook specific functions
  39  * in linux/fsnotify.h.  Those functions then in turn call here.  Here will call
  40  * out to all of the registered fsnotify_group.  Those groups can then use the
  41  * notification event in whatever means they feel necessary.
  42  */
  43 void fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is)
  44 {
  45         struct fsnotify_group *group;
  46         struct fsnotify_event *event = NULL;
  47         int idx;
  48
  49         if (list_empty(&fsnotify_groups))
  50                 return;
  51
  52         if (!(mask & fsnotify_mask))
  53                 return;
  54
  55         if (!(mask & to_tell->i_fsnotify_mask))
  56                 return;
  57         /*
  58          * SRCU!!  the groups list is very very much read only and the path is
  59          * very hot.  The VAST majority of events are not going to need to do
  60          * anything other than walk the list so it's crazy to pre-allocate.
  61          */
  62         idx = srcu_read_lock(&fsnotify_grp_srcu);
  63         list_for_each_entry_rcu(group, &fsnotify_groups, group_list) {
  64                 if (mask & group->mask) {
  65                         if (!group->ops->should_send_event(group, to_tell, mask))
  66                                 continue;
  67                         if (!event) {
  68                                 event = fsnotify_create_event(to_tell, mask, data, data_is);
  69                                 /* shit, we OOM'd and now we can't tell, maybe
  70                                  * someday someone else will want to do something
  71                                  * here */
  72                                 if (!event)
  73                                         break;
  74                         }
  75                         group->ops->handle_event(group, event);
  76                 }
  77         }
  78         srcu_read_unlock(&fsnotify_grp_srcu, idx);
  79         /*
  80          * fsnotify_create_event() took a reference so the event can't be cleaned
  81          * up while we are still trying to add it to lists, drop that one.
  82          */
  83         if (event)
  84                 fsnotify_put_event(event);
  85 }
  86 EXPORT_SYMBOL_GPL(fsnotify);
  87
  88 static __init int fsnotify_init(void)
  89 {
  90         return init_srcu_struct(&fsnotify_grp_srcu);
  91 }
  92 subsys_initcall(fsnotify_init);