LXR linux/fs/fs

   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 */
  12void set_fs_root(struct fs_struct *fs, struct path *path)
  13{
  14        struct path old_root;
  15
  16        write_lock(&fs->lock);
  17        old_root = fs->root;
  18        fs->root = *path;
  19        path_get(path);
  20        write_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 */
  29void set_fs_pwd(struct fs_struct *fs, struct path *path)
  30{
  31        struct path old_pwd;
  32
  33        write_lock(&fs->lock);
  34        old_pwd = fs->pwd;
  35        fs->pwd = *path;
  36        path_get(path);
  37        write_unlock(&fs->lock);
  38
  39        if (old_pwd.dentry)
  40                path_put(&old_pwd);
  41}
  42
  43void 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                        write_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                        write_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
  76void 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
  83void 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                write_lock(&fs->lock);
  91                tsk->fs = NULL;
  92                kill = !--fs->users;
  93                write_unlock(&fs->lock);
  94                task_unlock(tsk);
  95                if (kill)
  96                        free_fs_struct(fs);
  97        }
  98}
  99
 100struct 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                rwlock_init(&fs->lock);
 108                fs->umask = old->umask;
 109                read_lock(&old->lock);
 110                fs->root = old->root;
 111                path_get(&old->root);
 112                fs->pwd = old->pwd;
 113                path_get(&old->pwd);
 114                read_unlock(&old->lock);
 115        }
 116        return fs;
 117}
 118
 119int unshare_fs_struct(void)
 120{
 121        struct fs_struct *fs = current->fs;
 122        struct fs_struct *new_fs = copy_fs_struct(fs);
 123        int kill;
 124
 125        if (!new_fs)
 126                return -ENOMEM;
 127
 128        task_lock(current);
 129        write_lock(&fs->lock);
 130        kill = !--fs->users;
 131        current->fs = new_fs;
 132        write_unlock(&fs->lock);
 133        task_unlock(current);
 134
 135        if (kill)
 136                free_fs_struct(fs);
 137
 138        return 0;
 139}
 140EXPORT_SYMBOL_GPL(unshare_fs_struct);
 141
 142int current_umask(void)
 143{
 144        return current->fs->umask;
 145}
 146EXPORT_SYMBOL(current_umask);
 147
 148/* to be mentioned only in INIT_TASK */
 149struct fs_struct init_fs = {
 150        .users          = 1,
 151        .lock           = __RW_LOCK_UNLOCKED(init_fs.lock),
 152        .umask          = 0022,
 153};
 154
 155void daemonize_fs_struct(void)
 156{
 157        struct fs_struct *fs = current->fs;
 158
 159        if (fs) {
 160                int kill;
 161
 162                task_lock(current);
 163
 164                write_lock(&init_fs.lock);
 165                init_fs.users++;
 166                write_unlock(&init_fs.lock);
 167
 168                write_lock(&fs->lock);
 169                current->fs = &init_fs;
 170                kill = !--fs->users;
 171                write_unlock(&fs->lock);
 172
 173                task_unlock(current);
 174                if (kill)
 175                        free_fs_struct(fs);
 176        }
 177}
 178