Btrfs: Add BTRFS_IOC_SUBVOL_GETFLAGS/SETFLAGS ioctls
This allows us to set a snapshot or a subvolume readonly or writable
on the fly.
Usage:
Set BTRFS_SUBVOL_RDONLY of btrfs_ioctl_vol_arg_v2->flags, and then
call ioctl(BTRFS_IOCTL_SUBVOL_SETFLAGS);
Changelog for v3:
- Change to pass __u64 as ioctl parameter.
Changelog for v2:
- Add _GETFLAGS ioctl.
- Check if the passed fd is the root of a subvolume.
- Change the name from _SNAP_SETFLAGS to _SUBVOL_SETFLAGS.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f066ccb..ad19835 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1009,6 +1009,85 @@
return ret;
}
+static noinline int btrfs_ioctl_subvol_getflags(struct file *file,
+ void __user *arg)
+{
+ struct inode *inode = fdentry(file)->d_inode;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+ int ret = 0;
+ u64 flags = 0;
+
+ if (inode->i_ino != BTRFS_FIRST_FREE_OBJECTID)
+ return -EINVAL;
+
+ down_read(&root->fs_info->subvol_sem);
+ if (btrfs_root_readonly(root))
+ flags |= BTRFS_SUBVOL_RDONLY;
+ up_read(&root->fs_info->subvol_sem);
+
+ if (copy_to_user(arg, &flags, sizeof(flags)))
+ ret = -EFAULT;
+
+ return ret;
+}
+
+static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
+ void __user *arg)
+{
+ struct inode *inode = fdentry(file)->d_inode;
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+ struct btrfs_trans_handle *trans;
+ u64 root_flags;
+ u64 flags;
+ int ret = 0;
+
+ if (root->fs_info->sb->s_flags & MS_RDONLY)
+ return -EROFS;
+
+ if (inode->i_ino != BTRFS_FIRST_FREE_OBJECTID)
+ return -EINVAL;
+
+ if (copy_from_user(&flags, arg, sizeof(flags)))
+ return -EFAULT;
+
+ if (flags & ~BTRFS_SUBVOL_CREATE_ASYNC)
+ return -EINVAL;
+
+ if (flags & ~BTRFS_SUBVOL_RDONLY)
+ return -EOPNOTSUPP;
+
+ down_write(&root->fs_info->subvol_sem);
+
+ /* nothing to do */
+ if (!!(flags & BTRFS_SUBVOL_RDONLY) == btrfs_root_readonly(root))
+ goto out;
+
+ root_flags = btrfs_root_flags(&root->root_item);
+ if (flags & BTRFS_SUBVOL_RDONLY)
+ btrfs_set_root_flags(&root->root_item,
+ root_flags | BTRFS_ROOT_SUBVOL_RDONLY);
+ else
+ btrfs_set_root_flags(&root->root_item,
+ root_flags & ~BTRFS_ROOT_SUBVOL_RDONLY);
+
+ trans = btrfs_start_transaction(root, 1);
+ if (IS_ERR(trans)) {
+ ret = PTR_ERR(trans);
+ goto out_reset;
+ }
+
+ ret = btrfs_update_root(trans, root,
+ &root->root_key, &root->root_item);
+
+ btrfs_commit_transaction(trans, root);
+out_reset:
+ if (ret)
+ btrfs_set_root_flags(&root->root_item, root_flags);
+out:
+ up_write(&root->fs_info->subvol_sem);
+ return ret;
+}
+
/*
* helper to check if the subvolume references other subvolumes
*/
@@ -2282,6 +2361,10 @@
return btrfs_ioctl_snap_create(file, argp, 1);
case BTRFS_IOC_SNAP_DESTROY:
return btrfs_ioctl_snap_destroy(file, argp);
+ case BTRFS_IOC_SUBVOL_GETFLAGS:
+ return btrfs_ioctl_subvol_getflags(file, argp);
+ case BTRFS_IOC_SUBVOL_SETFLAGS:
+ return btrfs_ioctl_subvol_setflags(file, argp);
case BTRFS_IOC_DEFAULT_SUBVOL:
return btrfs_ioctl_default_subvol(file, argp);
case BTRFS_IOC_DEFRAG: