1 files changed, 90 insertions, 0 deletions

diff --git a/fs/super.c b/fs/super.c
index c248ac6a1a21..89afca5055ab 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -944,6 +944,96 @@ out:
 
 EXPORT_SYMBOL_GPL(vfs_kern_mount);
 
+/**
+ * freeze_super -- lock the filesystem and force it into a consistent state
+ * @super: the super to lock
+ *
+ * Syncs the super to make sure the filesystem is consistent and calls the fs's
+ * freeze_fs.  Subsequent calls to this without first thawing the fs will return
+ * -EBUSY.
+ */
+int freeze_super(struct super_block *sb)
+{
+        int ret;
+
+        atomic_inc(&sb->s_active);
+        down_write(&sb->s_umount);
+        if (sb->s_frozen) {
+                deactivate_locked_super(sb);
+                return -EBUSY;
+        }
+
+        if (sb->s_flags & MS_RDONLY) {
+                sb->s_frozen = SB_FREEZE_TRANS;
+                smp_wmb();
+                up_write(&sb->s_umount);
+                return 0;
+        }
+
+        sb->s_frozen = SB_FREEZE_WRITE;
+        smp_wmb();
+
+        sync_filesystem(sb);
+
+        sb->s_frozen = SB_FREEZE_TRANS;
+        smp_wmb();
+
+        sync_blockdev(sb->s_bdev);
+        if (sb->s_op->freeze_fs) {
+                ret = sb->s_op->freeze_fs(sb);
+                if (ret) {
+                        printk(KERN_ERR
+                                "VFS:Filesystem freeze failed\n");
+                        sb->s_frozen = SB_UNFROZEN;
+                        deactivate_locked_super(sb);
+                        return ret;
+                }
+        }
+        up_write(&sb->s_umount);
+        return 0;
+}
+EXPORT_SYMBOL(freeze_super);
+
+/**
+ * thaw_super -- unlock filesystem
+ * @sb: the super to thaw
+ *
+ * Unlocks the filesystem and marks it writeable again after freeze_super().
+ */
+int thaw_super(struct super_block *sb)
+{
+        int error;
+
+        down_write(&sb->s_umount);
+        if (sb->s_frozen == SB_UNFROZEN) {
+                up_write(&sb->s_umount);
+                return -EINVAL;
+        }
+
+        if (sb->s_flags & MS_RDONLY)
+                goto out;
+
+        if (sb->s_op->unfreeze_fs) {
+                error = sb->s_op->unfreeze_fs(sb);
+                if (error) {
+                        printk(KERN_ERR
+                                "VFS:Filesystem thaw failed\n");
+                        sb->s_frozen = SB_FREEZE_TRANS;
+                        up_write(&sb->s_umount);
+                        return error;
+                }
+        }
+
+out:
+        sb->s_frozen = SB_UNFROZEN;
+        smp_wmb();
+        wake_up(&sb->s_wait_unfrozen);
+        deactivate_locked_super(sb);
+
+        return 0;
+}
+EXPORT_SYMBOL(thaw_super);
+
 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
 {
         int err;