On 	wed, 28 Nov 2012 18:02:56 +0800, Anand Jain wrote:

On 11/28/2012 11:05 AM, Miao Xie wrote:

quoted

On wed, 28 Nov 2012 02:29:17 +0800, Anand jain wrote:

quoted

  /*

@@ -2441,6 +2443,14 @@ static inline bool btrfs_root_readonly(struct btrfs_root *root)
  {
      return (root->root_item.flags & cpu_to_le64(BTRFS_ROOT_SUBVOL_RDONLY)) != 0;
  }
+static inline char * btrfs_root_label(struct btrfs_root_item *root_item)
+{
+    return (root_item->label);
+}
+static inline void btrfs_root_set_label(struct btrfs_root_item *root_item, char *val)
+{
+    memcpy(root_item->label, val, BTRFS_SUBVOL_LABEL_SIZE);
+}

  /* struct btrfs_root_backup */
  BTRFS_SETGET_STACK_FUNCS(backup_tree_root, struct btrfs_root_backup,

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index e58bd9d..f0b3d9d 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c

@@ -3725,6 +3725,57 @@ static int btrfs_ioctl_set_label(struct btrfs_root *root, void __user *arg)
      return 0;
  }

+static int btrfs_ioctl_subvol_getlabel(struct btrfs_root *root,
+                        void __user *arg)
+{
+    char *label;
+
+    label = btrfs_root_label(&root->root_item);
+    if (copy_to_user(arg, label, BTRFS_SUBVOL_LABEL_SIZE))
+        return -EFAULT;

we also need lock here.

 yes. wish memcpy is atomic.

quoted

quoted

+    return 0;
+}
+
+static int btrfs_ioctl_subvol_setlabel(struct file *file,
+                        void __user *arg)
+{
+    char label[BTRFS_SUBVOL_LABEL_SIZE+1];
+    struct btrfs_trans_handle *trans;
+    struct btrfs_root *root = BTRFS_I(fdentry(file)->d_inode)->root;
+    struct inode *inode = file->f_path.dentry->d_inode;
+    int ret;
+
+    if (btrfs_root_readonly(root))
+        return -EROFS;
+
+    if (!inode_owner_or_capable(inode))
+        return -EACCES;
+
+    ret = mnt_want_write_file(file);
+    if (ret)
+        return ret;
+
+    if (copy_from_user(label, arg, BTRFS_SUBVOL_LABEL_SIZE)) {
+        ret = -EFAULT;
+        goto out;
+    }
+
+    mutex_lock(&inode->i_mutex);

we should use a lock which belongs to the root not inode.

 I couldn't find an already defined lock which would exactly
 fit the purpose here. Do you have any idea ?

I thinks we may use ->root_times_lock, but we need change the name
to make it suitable for its role.

Thanks
Miao

Thanks, Anand


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