Re: [PATCH] xfs: get root inode correctly at bulkstat

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Dec 21, 2022 at 10:22:21AM -0500, Hironori Shiina wrote:
> The root inode number should be set to `breq->startino` for getting stat
> information of the root when XFS_BULK_IREQ_SPECIAL_ROOT is used.
> Otherwise, the inode search is started from 1
> (XFS_BULK_IREQ_SPECIAL_ROOT) and the inode with the lowest number in a
> filesystem is returned.
> 
> Fixes: bf3cb3944792 ("xfs: allow single bulkstat of special inodes")
> Signed-off-by: Hironori Shiina <shiina.hironori@fujitsu.com>

D'oh.  Nobody noticed this because .... the root dir is usually the
first inode in the first inode chunk, and XFS_BULK_IREQ_SPECIAL_ROOT==1,
so that usually lines us up to find the root dir.

Except in that weird case where we format with a big stripe alignment,
mount with zeroed stripe alignment, and then stuff gets allocated before
the ichunk containing the root inode, right?

> ---
>  fs/xfs/xfs_ioctl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 13f1b2add390..020111f0f2a2 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -780,7 +780,7 @@ xfs_bulk_ireq_setup(
>  
>  		switch (hdr->ino) {

I might change @hdr to be a const pointer to prevent further accidents
here when I commit this.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

>  		case XFS_BULK_IREQ_SPECIAL_ROOT:
> -			hdr->ino = mp->m_sb.sb_rootino;
> +			breq->startino = mp->m_sb.sb_rootino;
>  			break;
>  		default:
>  			return -EINVAL;
> -- 
> 2.38.1
>