fs/dnotify.c

   1 /*
   2  * Directory notifications for Linux.
   3  *
   4  * Copyright (C) 2000,2001,2002 Stephen Rothwell
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; either version 2, or (at your option) any
   9  * later version.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * General Public License for more details.
  15  */
  16 #include <linux/fs.h>
  17 #include <linux/module.h>
  18 #include <linux/sched.h>
  19 #include <linux/dnotify.h>
  20 #include <linux/init.h>
  21 #include <linux/spinlock.h>
  22 #include <linux/slab.h>
  23
  24 int dir_notify_enable __read_mostly = 1;
  25
  26 static struct kmem_cache *dn_cache __read_mostly;
  27
  28 static void redo_inode_mask(struct inode *inode)
  29 {
  30         unsigned long new_mask;
  31         struct dnotify_struct *dn;
  32
  33         new_mask = 0;
  34         for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next)
  35                 new_mask |= dn->dn_mask & ~DN_MULTISHOT;
  36         inode->i_dnotify_mask = new_mask;
  37 }
  38
  39 void dnotify_flush(struct file *filp, fl_owner_t id)
  40 {
  41         struct dnotify_struct *dn;
  42         struct dnotify_struct **prev;
  43         struct inode *inode;
  44
  45         inode = filp->f_dentry->d_inode;
  46         if (!S_ISDIR(inode->i_mode))
  47                 return;
  48         spin_lock(&inode->i_lock);
  49         prev = &inode->i_dnotify;
  50         while ((dn = *prev) != NULL) {
  51                 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
  52                         *prev = dn->dn_next;
  53                         redo_inode_mask(inode);
  54                         kmem_cache_free(dn_cache, dn);
  55                         break;
  56                 }
  57                 prev = &dn->dn_next;
  58         }
  59         spin_unlock(&inode->i_lock);
  60 }
  61
  62 int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
  63 {
  64         struct dnotify_struct *dn;
  65         struct dnotify_struct *odn;
  66         struct dnotify_struct **prev;
  67         struct inode *inode;
  68         fl_owner_t id = current->files;
  69         int error = 0;
  70
  71         if ((arg & ~DN_MULTISHOT) == 0) {
  72                 dnotify_flush(filp, id);
  73                 return 0;
  74         }
  75         if (!dir_notify_enable)
  76                 return -EINVAL;
  77         inode = filp->f_dentry->d_inode;
  78         if (!S_ISDIR(inode->i_mode))
  79                 return -ENOTDIR;
  80         dn = kmem_cache_alloc(dn_cache, GFP_KERNEL);
  81         if (dn == NULL)
  82                 return -ENOMEM;
  83         spin_lock(&inode->i_lock);
  84         prev = &inode->i_dnotify;
  85         while ((odn = *prev) != NULL) {
  86                 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
  87                         odn->dn_fd = fd;
  88                         odn->dn_mask |= arg;
  89                         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
  90                         goto out_free;
  91                 }
  92                 prev = &odn->dn_next;
  93         }
  94
  95         error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
  96         if (error)
  97                 goto out_free;
  98
  99         dn->dn_mask = arg;
 100         dn->dn_fd = fd;
 101         dn->dn_filp = filp;
 102         dn->dn_owner = id;
 103         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
 104         dn->dn_next = inode->i_dnotify;
 105         inode->i_dnotify = dn;
 106         spin_unlock(&inode->i_lock);
 107
 108         if (filp->f_op && filp->f_op->dir_notify)
 109                 return filp->f_op->dir_notify(filp, arg);
 110         return 0;
 111
 112 out_free:
 113         spin_unlock(&inode->i_lock);
 114         kmem_cache_free(dn_cache, dn);
 115         return error;
 116 }
 117
 118 void __inode_dir_notify(struct inode *inode, unsigned long event)
 119 {
 120         struct dnotify_struct * dn;
 121         struct dnotify_struct **prev;
 122         struct fown_struct *    fown;
 123         int                     changed = 0;
 124
 125         spin_lock(&inode->i_lock);
 126         prev = &inode->i_dnotify;
 127         while ((dn = *prev) != NULL) {
 128                 if ((dn->dn_mask & event) == 0) {
 129                         prev = &dn->dn_next;
 130                         continue;
 131                 }
 132                 fown = &dn->dn_filp->f_owner;
 133                 send_sigio(fown, dn->dn_fd, POLL_MSG);
 134                 if (dn->dn_mask & DN_MULTISHOT)
 135                         prev = &dn->dn_next;
 136                 else {
 137                         *prev = dn->dn_next;
 138                         changed = 1;
 139                         kmem_cache_free(dn_cache, dn);
 140                 }
 141         }
 142         if (changed)
 143                 redo_inode_mask(inode);
 144         spin_unlock(&inode->i_lock);
 145 }
 146
 147 EXPORT_SYMBOL(__inode_dir_notify);
 148
 149 /*
 150  * This is hopelessly wrong, but unfixable without API changes.  At
 151  * least it doesn't oops the kernel...
 152  *
 153  * To safely access ->d_parent we need to keep d_move away from it.  Use the
 154  * dentry's d_lock for this.
 155  */
 156 void dnotify_parent(struct dentry *dentry, unsigned long event)
 157 {
 158         struct dentry *parent;
 159
 160         if (!dir_notify_enable)
 161                 return;
 162
 163         spin_lock(&dentry->d_lock);
 164         parent = dentry->d_parent;
 165         if (parent->d_inode->i_dnotify_mask & event) {
 166                 dget(parent);
 167                 spin_unlock(&dentry->d_lock);
 168                 __inode_dir_notify(parent->d_inode, event);
 169                 dput(parent);
 170         } else {
 171                 spin_unlock(&dentry->d_lock);
 172         }
 173 }
 174 EXPORT_SYMBOL_GPL(dnotify_parent);
 175
 176 static int __init dnotify_init(void)
 177 {
 178         dn_cache = kmem_cache_create("dnotify_cache",
 179                 sizeof(struct dnotify_struct), 0, SLAB_PANIC, NULL, NULL);
 180         return 0;
 181 }
 182
 183 module_init(dnotify_init)