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 #include <linux/fdtable.h>
  24
  25 int dir_notify_enable __read_mostly = 1;
  26
  27 static struct kmem_cache *dn_cache __read_mostly;
  28
  29 static void redo_inode_mask(struct inode *inode)
  30 {
  31         unsigned long new_mask;
  32         struct dnotify_struct *dn;
  33
  34         new_mask = 0;
  35         for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next)
  36                 new_mask |= dn->dn_mask & ~DN_MULTISHOT;
  37         inode->i_dnotify_mask = new_mask;
  38 }
  39
  40 void dnotify_flush(struct file *filp, fl_owner_t id)
  41 {
  42         struct dnotify_struct *dn;
  43         struct dnotify_struct **prev;
  44         struct inode *inode;
  45
  46         inode = filp->f_path.dentry->d_inode;
  47         if (!S_ISDIR(inode->i_mode))
  48                 return;
  49         spin_lock(&inode->i_lock);
  50         prev = &inode->i_dnotify;
  51         while ((dn = *prev) != NULL) {
  52                 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
  53                         *prev = dn->dn_next;
  54                         redo_inode_mask(inode);
  55                         kmem_cache_free(dn_cache, dn);
  56                         break;
  57                 }
  58                 prev = &dn->dn_next;
  59         }
  60         spin_unlock(&inode->i_lock);
  61 }
  62
  63 int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
  64 {
  65         struct dnotify_struct *dn;
  66         struct dnotify_struct *odn;
  67         struct dnotify_struct **prev;
  68         struct inode *inode;
  69         fl_owner_t id = current->files;
  70         struct file *f;
  71         int error = 0;
  72
  73         if ((arg & ~DN_MULTISHOT) == 0) {
  74                 dnotify_flush(filp, id);
  75                 return 0;
  76         }
  77         if (!dir_notify_enable)
  78                 return -EINVAL;
  79         inode = filp->f_path.dentry->d_inode;
  80         if (!S_ISDIR(inode->i_mode))
  81                 return -ENOTDIR;
  82         dn = kmem_cache_alloc(dn_cache, GFP_KERNEL);
  83         if (dn == NULL)
  84                 return -ENOMEM;
  85         spin_lock(&inode->i_lock);
  86         prev = &inode->i_dnotify;
  87         while ((odn = *prev) != NULL) {
  88                 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
  89                         odn->dn_fd = fd;
  90                         odn->dn_mask |= arg;
  91                         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
  92                         goto out_free;
  93                 }
  94                 prev = &odn->dn_next;
  95         }
  96
  97         rcu_read_lock();
  98         f = fcheck(fd);
  99         rcu_read_unlock();
 100         /* we'd lost the race with close(), sod off silently */
 101         /* note that inode->i_lock prevents reordering problems
 102          * between accesses to descriptor table and ->i_dnotify */
 103         if (f != filp)
 104                 goto out_free;
 105
 106         error = __f_setown(filp, task_pid(current), PIDTYPE_PID, 0);
 107         if (error)
 108                 goto out_free;
 109
 110         dn->dn_mask = arg;
 111         dn->dn_fd = fd;
 112         dn->dn_filp = filp;
 113         dn->dn_owner = id;
 114         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
 115         dn->dn_next = inode->i_dnotify;
 116         inode->i_dnotify = dn;
 117         spin_unlock(&inode->i_lock);
 118
 119         if (filp->f_op && filp->f_op->dir_notify)
 120                 return filp->f_op->dir_notify(filp, arg);
 121         return 0;
 122
 123 out_free:
 124         spin_unlock(&inode->i_lock);
 125         kmem_cache_free(dn_cache, dn);
 126         return error;
 127 }
 128
 129 void __inode_dir_notify(struct inode *inode, unsigned long event)
 130 {
 131         struct dnotify_struct * dn;
 132         struct dnotify_struct **prev;
 133         struct fown_struct *    fown;
 134         int                     changed = 0;
 135
 136         spin_lock(&inode->i_lock);
 137         prev = &inode->i_dnotify;
 138         while ((dn = *prev) != NULL) {
 139                 if ((dn->dn_mask & event) == 0) {
 140                         prev = &dn->dn_next;
 141                         continue;
 142                 }
 143                 fown = &dn->dn_filp->f_owner;
 144                 send_sigio(fown, dn->dn_fd, POLL_MSG);
 145                 if (dn->dn_mask & DN_MULTISHOT)
 146                         prev = &dn->dn_next;
 147                 else {
 148                         *prev = dn->dn_next;
 149                         changed = 1;
 150                         kmem_cache_free(dn_cache, dn);
 151                 }
 152         }
 153         if (changed)
 154                 redo_inode_mask(inode);
 155         spin_unlock(&inode->i_lock);
 156 }
 157
 158 EXPORT_SYMBOL(__inode_dir_notify);
 159
 160 /*
 161  * This is hopelessly wrong, but unfixable without API changes.  At
 162  * least it doesn't oops the kernel...
 163  *
 164  * To safely access ->d_parent we need to keep d_move away from it.  Use the
 165  * dentry's d_lock for this.
 166  */
 167 void dnotify_parent(struct dentry *dentry, unsigned long event)
 168 {
 169         struct dentry *parent;
 170
 171         if (!dir_notify_enable)
 172                 return;
 173
 174         spin_lock(&dentry->d_lock);
 175         parent = dentry->d_parent;
 176         if (parent->d_inode->i_dnotify_mask & event) {
 177                 dget(parent);
 178                 spin_unlock(&dentry->d_lock);
 179                 __inode_dir_notify(parent->d_inode, event);
 180                 dput(parent);
 181         } else {
 182                 spin_unlock(&dentry->d_lock);
 183         }
 184 }
 185 EXPORT_SYMBOL_GPL(dnotify_parent);
 186
 187 static int __init dnotify_init(void)
 188 {
 189         dn_cache = kmem_cache_create("dnotify_cache",
 190                 sizeof(struct dnotify_struct), 0, SLAB_PANIC, NULL);
 191         return 0;
 192 }
 193
 194 module_init(dnotify_init)