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 #include <linux/file.h>
23
24 extern void send_sigio(struct fown_struct *fown, int fd, int band);
25
26 int dir_notify_enable = 1;
27
28 static rwlock_t dn_lock = RW_LOCK_UNLOCKED;
29 static kmem_cache_t *dn_cache;
30
redo_inode_mask(struct inode * inode)31 static void redo_inode_mask(struct inode *inode)
32 {
33 unsigned long new_mask;
34 struct dnotify_struct *dn;
35
36 new_mask = 0;
37 for (dn = inode->i_dnotify; dn != NULL; dn = dn->dn_next)
38 new_mask |= dn->dn_mask & ~DN_MULTISHOT;
39 inode->i_dnotify_mask = new_mask;
40 }
41
dnotify_flush(struct file * filp,fl_owner_t id)42 void dnotify_flush(struct file *filp, fl_owner_t id)
43 {
44 struct dnotify_struct *dn;
45 struct dnotify_struct **prev;
46 struct inode *inode;
47
48 inode = filp->f_dentry->d_inode;
49 if (!S_ISDIR(inode->i_mode))
50 return;
51 write_lock(&dn_lock);
52 prev = &inode->i_dnotify;
53 while ((dn = *prev) != NULL) {
54 if ((dn->dn_owner == id) && (dn->dn_filp == filp)) {
55 *prev = dn->dn_next;
56 redo_inode_mask(inode);
57 kmem_cache_free(dn_cache, dn);
58 break;
59 }
60 prev = &dn->dn_next;
61 }
62 write_unlock(&dn_lock);
63 }
64
fcntl_dirnotify(int fd,struct file * filp,unsigned long arg)65 int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg)
66 {
67 struct dnotify_struct *dn;
68 struct dnotify_struct *odn;
69 struct dnotify_struct **prev;
70 struct inode *inode;
71 fl_owner_t id = current->files;
72 struct file *f;
73
74 if ((arg & ~DN_MULTISHOT) == 0) {
75 dnotify_flush(filp, id);
76 return 0;
77 }
78 if (!dir_notify_enable)
79 return -EINVAL;
80 inode = filp->f_dentry->d_inode;
81 if (!S_ISDIR(inode->i_mode))
82 return -ENOTDIR;
83 dn = kmem_cache_alloc(dn_cache, SLAB_KERNEL);
84 if (dn == NULL)
85 return -ENOMEM;
86 write_lock(&dn_lock);
87 prev = &inode->i_dnotify;
88 while ((odn = *prev) != NULL) {
89 if ((odn->dn_owner == id) && (odn->dn_filp == filp)) {
90 odn->dn_fd = fd;
91 odn->dn_mask |= arg;
92 inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
93 kmem_cache_free(dn_cache, dn);
94 goto out;
95 }
96 prev = &odn->dn_next;
97 }
98
99 /* we'd lost the race with close(), sod off silently */
100 read_lock(¤t->files->file_lock);
101 f = fcheck(fd);
102 read_unlock(¤t->files->file_lock);
103 if (f != filp) {
104 kmem_cache_free(dn_cache, dn);
105 goto out;
106 }
107
108 filp->f_owner.pid = current->pid;
109 filp->f_owner.uid = current->uid;
110 filp->f_owner.euid = current->euid;
111 dn->dn_mask = arg;
112 dn->dn_fd = fd;
113 dn->dn_filp = filp;
114 dn->dn_owner = id;
115 inode->i_dnotify_mask |= arg & ~DN_MULTISHOT;
116 dn->dn_next = inode->i_dnotify;
117 inode->i_dnotify = dn;
118 out:
119 write_unlock(&dn_lock);
120 return 0;
121 }
122
__inode_dir_notify(struct inode * inode,unsigned long event)123 void __inode_dir_notify(struct inode *inode, unsigned long event)
124 {
125 struct dnotify_struct * dn;
126 struct dnotify_struct **prev;
127 struct fown_struct * fown;
128 int changed = 0;
129
130 write_lock(&dn_lock);
131 prev = &inode->i_dnotify;
132 while ((dn = *prev) != NULL) {
133 if ((dn->dn_mask & event) == 0) {
134 prev = &dn->dn_next;
135 continue;
136 }
137 fown = &dn->dn_filp->f_owner;
138 if (fown->pid)
139 send_sigio(fown, dn->dn_fd, POLL_MSG);
140 if (dn->dn_mask & DN_MULTISHOT)
141 prev = &dn->dn_next;
142 else {
143 *prev = dn->dn_next;
144 changed = 1;
145 kmem_cache_free(dn_cache, dn);
146 }
147 }
148 if (changed)
149 redo_inode_mask(inode);
150 write_unlock(&dn_lock);
151 }
152
dnotify_init(void)153 static int __init dnotify_init(void)
154 {
155 dn_cache = kmem_cache_create("dnotify_cache",
156 sizeof(struct dnotify_struct), 0, 0, NULL, NULL);
157 if (!dn_cache)
158 panic("cannot create dnotify slab cache");
159 return 0;
160 }
161
162 module_init(dnotify_init)
163