fs: dcache scale dentry refcount
[linux-2.6.git] / fs / fs_struct.c
1 #include <linux/module.h>
2 #include <linux/sched.h>
3 #include <linux/fs.h>
4 #include <linux/path.h>
5 #include <linux/slab.h>
6 #include <linux/fs_struct.h>
7
8 /*
9  * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
10  * It can block.
11  */
12 void set_fs_root(struct fs_struct *fs, struct path *path)
13 {
14         struct path old_root;
15
16         spin_lock(&fs->lock);
17         old_root = fs->root;
18         fs->root = *path;
19         path_get(path);
20         spin_unlock(&fs->lock);
21         if (old_root.dentry)
22                 path_put(&old_root);
23 }
24
25 /*
26  * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
27  * It can block.
28  */
29 void set_fs_pwd(struct fs_struct *fs, struct path *path)
30 {
31         struct path old_pwd;
32
33         spin_lock(&fs->lock);
34         old_pwd = fs->pwd;
35         fs->pwd = *path;
36         path_get(path);
37         spin_unlock(&fs->lock);
38
39         if (old_pwd.dentry)
40                 path_put(&old_pwd);
41 }
42
43 void chroot_fs_refs(struct path *old_root, struct path *new_root)
44 {
45         struct task_struct *g, *p;
46         struct fs_struct *fs;
47         int count = 0;
48
49         read_lock(&tasklist_lock);
50         do_each_thread(g, p) {
51                 task_lock(p);
52                 fs = p->fs;
53                 if (fs) {
54                         spin_lock(&fs->lock);
55                         if (fs->root.dentry == old_root->dentry
56                             && fs->root.mnt == old_root->mnt) {
57                                 path_get(new_root);
58                                 fs->root = *new_root;
59                                 count++;
60                         }
61                         if (fs->pwd.dentry == old_root->dentry
62                             && fs->pwd.mnt == old_root->mnt) {
63                                 path_get(new_root);
64                                 fs->pwd = *new_root;
65                                 count++;
66                         }
67                         spin_unlock(&fs->lock);
68                 }
69                 task_unlock(p);
70         } while_each_thread(g, p);
71         read_unlock(&tasklist_lock);
72         while (count--)
73                 path_put(old_root);
74 }
75
76 void free_fs_struct(struct fs_struct *fs)
77 {
78         path_put(&fs->root);
79         path_put(&fs->pwd);
80         kmem_cache_free(fs_cachep, fs);
81 }
82
83 void exit_fs(struct task_struct *tsk)
84 {
85         struct fs_struct *fs = tsk->fs;
86
87         if (fs) {
88                 int kill;
89                 task_lock(tsk);
90                 spin_lock(&fs->lock);
91                 tsk->fs = NULL;
92                 kill = !--fs->users;
93                 spin_unlock(&fs->lock);
94                 task_unlock(tsk);
95                 if (kill)
96                         free_fs_struct(fs);
97         }
98 }
99
100 struct fs_struct *copy_fs_struct(struct fs_struct *old)
101 {
102         struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
103         /* We don't need to lock fs - think why ;-) */
104         if (fs) {
105                 fs->users = 1;
106                 fs->in_exec = 0;
107                 spin_lock_init(&fs->lock);
108                 fs->umask = old->umask;
109                 get_fs_root_and_pwd(old, &fs->root, &fs->pwd);
110         }
111         return fs;
112 }
113
114 int unshare_fs_struct(void)
115 {
116         struct fs_struct *fs = current->fs;
117         struct fs_struct *new_fs = copy_fs_struct(fs);
118         int kill;
119
120         if (!new_fs)
121                 return -ENOMEM;
122
123         task_lock(current);
124         spin_lock(&fs->lock);
125         kill = !--fs->users;
126         current->fs = new_fs;
127         spin_unlock(&fs->lock);
128         task_unlock(current);
129
130         if (kill)
131                 free_fs_struct(fs);
132
133         return 0;
134 }
135 EXPORT_SYMBOL_GPL(unshare_fs_struct);
136
137 int current_umask(void)
138 {
139         return current->fs->umask;
140 }
141 EXPORT_SYMBOL(current_umask);
142
143 /* to be mentioned only in INIT_TASK */
144 struct fs_struct init_fs = {
145         .users          = 1,
146         .lock           = __SPIN_LOCK_UNLOCKED(init_fs.lock),
147         .umask          = 0022,
148 };
149
150 void daemonize_fs_struct(void)
151 {
152         struct fs_struct *fs = current->fs;
153
154         if (fs) {
155                 int kill;
156
157                 task_lock(current);
158
159                 spin_lock(&init_fs.lock);
160                 init_fs.users++;
161                 spin_unlock(&init_fs.lock);
162
163                 spin_lock(&fs->lock);
164                 current->fs = &init_fs;
165                 kill = !--fs->users;
166                 spin_unlock(&fs->lock);
167
168                 task_unlock(current);
169                 if (kill)
170                         free_fs_struct(fs);
171         }
172 }