1 files changed, 177 insertions, 0 deletions

diff --git a/fs/fs_struct.c b/fs/fs_struct.c
new file mode 100644
index 000000000000..eee059052db5
--- /dev/null
+++ b/fs/fs_struct.c
@@ -0,0 +1,177 @@
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/fs.h>
+#include <linux/path.h>
+#include <linux/slab.h>
+#include <linux/fs_struct.h>
+
+/*
+ * Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
+ * It can block.
+ */
+void set_fs_root(struct fs_struct *fs, struct path *path)
+{
+        struct path old_root;
+
+        write_lock(&fs->lock);
+        old_root = fs->root;
+        fs->root = *path;
+        path_get(path);
+        write_unlock(&fs->lock);
+        if (old_root.dentry)
+                path_put(&old_root);
+}
+
+/*
+ * Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
+ * It can block.
+ */
+void set_fs_pwd(struct fs_struct *fs, struct path *path)
+{
+        struct path old_pwd;
+
+        write_lock(&fs->lock);
+        old_pwd = fs->pwd;
+        fs->pwd = *path;
+        path_get(path);
+        write_unlock(&fs->lock);
+
+        if (old_pwd.dentry)
+                path_put(&old_pwd);
+}
+
+void chroot_fs_refs(struct path *old_root, struct path *new_root)
+{
+        struct task_struct *g, *p;
+        struct fs_struct *fs;
+        int count = 0;
+
+        read_lock(&tasklist_lock);
+        do_each_thread(g, p) {
+                task_lock(p);
+                fs = p->fs;
+                if (fs) {
+                        write_lock(&fs->lock);
+                        if (fs->root.dentry == old_root->dentry
+                            && fs->root.mnt == old_root->mnt) {
+                                path_get(new_root);
+                                fs->root = *new_root;
+                                count++;
+                        }
+                        if (fs->pwd.dentry == old_root->dentry
+                            && fs->pwd.mnt == old_root->mnt) {
+                                path_get(new_root);
+                                fs->pwd = *new_root;
+                                count++;
+                        }
+                        write_unlock(&fs->lock);
+                }
+                task_unlock(p);
+        } while_each_thread(g, p);
+        read_unlock(&tasklist_lock);
+        while (count--)
+                path_put(old_root);
+}
+
+void free_fs_struct(struct fs_struct *fs)
+{
+        path_put(&fs->root);
+        path_put(&fs->pwd);
+        kmem_cache_free(fs_cachep, fs);
+}
+
+void exit_fs(struct task_struct *tsk)
+{
+        struct fs_struct *fs = tsk->fs;
+
+        if (fs) {
+                int kill;
+                task_lock(tsk);
+                write_lock(&fs->lock);
+                tsk->fs = NULL;
+                kill = !--fs->users;
+                write_unlock(&fs->lock);
+                task_unlock(tsk);
+                if (kill)
+                        free_fs_struct(fs);
+        }
+}
+
+struct fs_struct *copy_fs_struct(struct fs_struct *old)
+{
+        struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
+        /* We don't need to lock fs - think why ;-) */
+        if (fs) {
+                fs->users = 1;
+                fs->in_exec = 0;
+                rwlock_init(&fs->lock);
+                fs->umask = old->umask;
+                read_lock(&old->lock);
+                fs->root = old->root;
+                path_get(&old->root);
+                fs->pwd = old->pwd;
+                path_get(&old->pwd);
+                read_unlock(&old->lock);
+        }
+        return fs;
+}
+
+int unshare_fs_struct(void)
+{
+        struct fs_struct *fs = current->fs;
+        struct fs_struct *new_fs = copy_fs_struct(fs);
+        int kill;
+
+        if (!new_fs)
+                return -ENOMEM;
+
+        task_lock(current);
+        write_lock(&fs->lock);
+        kill = !--fs->users;
+        current->fs = new_fs;
+        write_unlock(&fs->lock);
+        task_unlock(current);
+
+        if (kill)
+                free_fs_struct(fs);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(unshare_fs_struct);
+
+int current_umask(void)
+{
+        return current->fs->umask;
+}
+EXPORT_SYMBOL(current_umask);
+
+/* to be mentioned only in INIT_TASK */
+struct fs_struct init_fs = {
+        .users          = 1,
+        .lock           = __RW_LOCK_UNLOCKED(init_fs.lock),
+        .umask          = 0022,
+};
+
+void daemonize_fs_struct(void)
+{
+        struct fs_struct *fs = current->fs;
+
+        if (fs) {
+                int kill;
+
+                task_lock(current);
+
+                write_lock(&init_fs.lock);
+                init_fs.users++;
+                write_unlock(&init_fs.lock);
+
+                write_lock(&fs->lock);
+                current->fs = &init_fs;
+                kill = !--fs->users;
+                write_unlock(&fs->lock);
+
+                task_unlock(current);
+                if (kill)
+                        free_fs_struct(fs);
+        }
+}