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 = 1;
  25
  26 static rwlock_t dn_lock = RW_LOCK_UNLOCKED;
  27 static kmem_cache_t *dn_cache;
  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_dentry->d_inode;
  47         if (!S_ISDIR(inode->i_mode))
  48                 return;
  49         write_lock(&dn_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         write_unlock(&dn_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         int error = 0;
  71
  72         if ((arg & ~DN_MULTISHOT) == 0) {
  73                 dnotify_flush(filp, id);
  74                 return 0;
  75         }
  76         if (!dir_notify_enable)
  77                 return -EINVAL;
  78         inode = filp->f_dentry->d_inode;
  79         if (!S_ISDIR(inode->i_mode))
  80                 return -ENOTDIR;
  81         dn = kmem_cache_alloc(dn_cache, SLAB_KERNEL);
  82         if (dn == NULL)
  83                 return -ENOMEM;
  84         write_lock(&dn_lock);
  85         prev = &inode->i_dnotify;
  86         while ((odn = *prev) != NULL) {
  87                 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
  88                         odn->dn_fd = fd;
  89                         odn->dn_mask |= arg;
  90                         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
  91                         goto out_free;
  92                 }
  93                 prev = &odn->dn_next;
  94         }
  95
  96         error = f_setown(filp, current->pid, 0);
  97         if (error)
  98                 goto out_free;
  99
 100         dn->dn_mask = arg;
 101         dn->dn_fd = fd;
 102         dn->dn_filp = filp;
 103         dn->dn_owner = id;
 104         inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
 105         dn->dn_next = inode->i_dnotify;
 106         inode->i_dnotify = dn;
 107 out:
 108         write_unlock(&dn_lock);
 109         return error;
 110 out_free:
 111         kmem_cache_free(dn_cache, dn);
 112         goto out;
 113 }
 114
 115 void __inode_dir_notify(struct inode *inode, unsigned long event)
 116 {
 117         struct dnotify_struct * dn;
 118         struct dnotify_struct **prev;
 119         struct fown_struct *    fown;
 120         int                     changed = 0;
 121
 122         write_lock(&dn_lock);
 123         prev = &inode->i_dnotify;
 124         while ((dn = *prev) != NULL) {
 125                 if ((dn->dn_mask & event) == 0) {
 126                         prev = &dn->dn_next;
 127                         continue;
 128                 }
 129                 fown = &dn->dn_filp->f_owner;
 130                 send_sigio(fown, dn->dn_fd, POLL_MSG);
 131                 if (dn->dn_mask & DN_MULTISHOT)
 132                         prev = &dn->dn_next;
 133                 else {
 134                         *prev = dn->dn_next;
 135                         changed = 1;
 136                         kmem_cache_free(dn_cache, dn);
 137                 }
 138         }
 139         if (changed)
 140                 redo_inode_mask(inode);
 141         write_unlock(&dn_lock);
 142 }
 143
 144 EXPORT_SYMBOL(__inode_dir_notify);
 145
 146 /*
 147  * This is hopelessly wrong, but unfixable without API changes.  At
 148  * least it doesn't oops the kernel...
 149  *
 150  * To safely access ->d_parent we need to keep d_move away from it.  Use the
 151  * dentry's d_lock for this.
 152  */
 153 void dnotify_parent(struct dentry *dentry, unsigned long event)
 154 {
 155         struct dentry *parent;
 156
 157         if (!dir_notify_enable)
 158                 return;
 159
 160         spin_lock(&dentry->d_lock);
 161         parent = dentry->d_parent;
 162         if (parent->d_inode->i_dnotify_mask & event) {
 163                 dget(parent);
 164                 spin_unlock(&dentry->d_lock);
 165                 __inode_dir_notify(parent->d_inode, event);
 166                 dput(parent);
 167         } else {
 168                 spin_unlock(&dentry->d_lock);
 169         }
 170 }
 171 EXPORT_SYMBOL_GPL(dnotify_parent);
 172
 173 static int __init dnotify_init(void)
 174 {
 175         dn_cache = kmem_cache_create("dnotify_cache",
 176                 sizeof(struct dnotify_struct), 0, SLAB_PANIC, NULL, NULL);
 177         return 0;
 178 }
 179
 180 module_init(dnotify_init)