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/sched.h>
  18 #include <linux/dnotify.h>
  19 #include <linux/init.h>
  20 #include <linux/spinlock.h>
  21 #include <linux/slab.h>
  22
  23 extern void send_sigio(struct fown_struct *fown, int fd, int band);
  24
  25 int dir_notify_enable = 1;
  26
  27 static rwlock_t dn_lock = RW_LOCK_UNLOCKED;
  28 static kmem_cache_t *dn_cache;
  29
  30 static void redo_inode_mask(struct inode *inode)
  31 {
  32         unsigned long new_mask;
  33         struct dnotify_struct *dn;
  34
  35         new_mask = 0;
  36         for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next)
  37                 new_mask |= dn->dn_mask & ~DN_MULTISHOT;
  38         inode->i_dnotify_mask = new_mask;
  39 }
  40
  41 void dnotify_flush(struct file *filp, fl_owner_t id)
  42 {
  43         struct dnotify_struct *dn;
  44         struct dnotify_struct **prev;
  45         struct inode *inode;
  46
  47         inode = filp->f_dentry->d_inode;
  48         if (!S_ISDIR(inode->i_mode))
  49                 return;
  50         write_lock(&dn_lock);
  51         prev = &inode->i_dnotify;
  52         while ((dn = *prev) != NULL) {
  53                 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
  54                         *prev = dn->dn_next;
  55                         redo_inode_mask(inode);
  56                         kmem_cache_free(dn_cache, dn);
  57                         break;
  58                 }
  59                 prev = &dn->dn_next;
  60         }
  61         write_unlock(&dn_lock);
  62 }
  63
  64 int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
  65 {
  66         struct dnotify_struct *dn;
  67         struct dnotify_struct *odn;
  68         struct dnotify_struct **prev;
  69         struct inode *inode;
  70         fl_owner_t id = current->files;
  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                         kmem_cache_free(dn_cache, dn);
  92                         goto out;
  93                 }
  94                 prev = &odn->dn_next;
  95         }
  96         filp->f_owner.pid = current->pid;
  97         filp->f_owner.uid = current->uid;
  98         filp->f_owner.euid = current->euid;
  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 out:
 107         write_unlock(&dn_lock);
 108         return 0;
 109 }
 110
 111 void __inode_dir_notify(struct inode *inode, unsigned long event)
 112 {
 113         struct dnotify_struct * dn;
 114         struct dnotify_struct **prev;
 115         struct fown_struct *    fown;
 116         int                     changed = 0;
 117
 118         write_lock(&dn_lock);
 119         prev = &inode->i_dnotify;
 120         while ((dn = *prev) != NULL) {
 121                 if ((dn->dn_mask & event) == 0) {
 122                         prev = &dn->dn_next;
 123                         continue;
 124                 }
 125                 fown = &dn->dn_filp->f_owner;
 126                 if (fown->pid)
 127                         send_sigio(fown, dn->dn_fd, POLL_MSG);
 128                 if (dn->dn_mask & DN_MULTISHOT)
 129                         prev = &dn->dn_next;
 130                 else {
 131                         *prev = dn->dn_next;
 132                         changed = 1;
 133                         kmem_cache_free(dn_cache, dn);
 134                 }
 135         }
 136         if (changed)
 137                 redo_inode_mask(inode);
 138         write_unlock(&dn_lock);
 139 }
 140
 141 static int __init dnotify_init(void)
 142 {
 143         dn_cache = kmem_cache_create("dnotify_cache",
 144                 sizeof(struct dnotify_struct), 0, 0, NULL, NULL);
 145         if (!dn_cache)
 146                 panic("cannot create dnotify slab cache");
 147         return 0;
 148 }
 149
 150 module_init(dnotify_init)