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 return 0; 119 120 out_free: 121 spin_unlock(&inode->i_lock); 122 kmem_cache_free(dn_cache, dn); 123 return error; 124 } 125 126 void __inode_dir_notify(struct inode *inode, unsigned long event) 127 { 128 struct dnotify_struct * dn; 129 struct dnotify_struct **prev; 130 struct fown_struct * fown; 131 int changed = 0; 132 133 spin_lock(&inode->i_lock); 134 prev = &inode->i_dnotify; 135 while ((dn = *prev) != NULL) { 136 if ((dn->dn_mask & event) == 0) { 137 prev = &dn->dn_next; 138 continue; 139 } 140 fown = &dn->dn_filp->f_owner; 141 send_sigio(fown, dn->dn_fd, POLL_MSG); 142 if (dn->dn_mask & DN_MULTISHOT) 143 prev = &dn->dn_next; 144 else { 145 *prev = dn->dn_next; 146 changed = 1; 147 kmem_cache_free(dn_cache, dn); 148 } 149 } 150 if (changed) 151 redo_inode_mask(inode); 152 spin_unlock(&inode->i_lock); 153 } 154 155 EXPORT_SYMBOL(__inode_dir_notify); 156 157 /* 158 * This is hopelessly wrong, but unfixable without API changes. At 159 * least it doesn't oops the kernel... 160 * 161 * To safely access ->d_parent we need to keep d_move away from it. Use the 162 * dentry's d_lock for this. 163 */ 164 void dnotify_parent(struct dentry *dentry, unsigned long event) 165 { 166 struct dentry *parent; 167 168 if (!dir_notify_enable) 169 return; 170 171 spin_lock(&dentry->d_lock); 172 parent = dentry->d_parent; 173 if (parent->d_inode->i_dnotify_mask & event) { 174 dget(parent); 175 spin_unlock(&dentry->d_lock); 176 __inode_dir_notify(parent->d_inode, event); 177 dput(parent); 178 } else { 179 spin_unlock(&dentry->d_lock); 180 } 181 } 182 EXPORT_SYMBOL_GPL(dnotify_parent); 183 184 static int __init dnotify_init(void) 185 { 186 dn_cache = kmem_cache_create("dnotify_cache", 187 sizeof(struct dnotify_struct), 0, SLAB_PANIC, NULL); 188 return 0; 189 } 190 191 module_init(dnotify_init) 192