On Wed, Jul 03, 2019 at 08:34:54AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Create a new ireq flag (for single bulkstats) that enables userspace to
> ask us for a special inode number instead of interpreting @ino as a
> literal inode number. This enables us to query the root inode easily.
>
> The reason for adding the ability to query specifically the root
> directory inode is that certain programs (xfsdump and xfsrestore) want
> to confirm when they've been pointed to the root directory. The
> userspace code assumes the root directory is always the first result
> from calling bulkstat with lastino == 0, but this isn't true if the
> (initial btree roots + initial AGFL + inode alignment padding) is itself
> long enough to be allocated to new inodes if all of those blocks should
> happen to be free at the same time. Rather than make userspace guess
> at internal filesystem state, we provide a direct query.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> Reviewed-by: Allison Collins <allison.henderson@xxxxxxxxxx>
> ---
> v2: elaborate on why we are adding this new ireq flag
> ---
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> fs/xfs/libxfs/xfs_fs.h | 11 ++++++++++-
> fs/xfs/xfs_ioctl.c | 10 ++++++++++
> 2 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
> index 77c06850ac52..1489bce07d66 100644
> --- a/fs/xfs/libxfs/xfs_fs.h
> +++ b/fs/xfs/libxfs/xfs_fs.h
> @@ -482,7 +482,16 @@ struct xfs_ireq {
> uint64_t reserved[2]; /* must be zero */
> };
>
> -#define XFS_IREQ_FLAGS_ALL (0)
> +/*
> + * The @ino value is a special value, not a literal inode number. See the
> + * XFS_IREQ_SPECIAL_* values below.
> + */
> +#define XFS_IREQ_SPECIAL (1 << 0)
> +
> +#define XFS_IREQ_FLAGS_ALL (XFS_IREQ_SPECIAL)
> +
> +/* Operate on the root directory inode. */
> +#define XFS_IREQ_SPECIAL_ROOT (1)
>
> /*
> * ioctl structures for v5 bulkstat and inumbers requests
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index ba9a99b7860f..11ccfc5611bf 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -952,6 +952,16 @@ xfs_ireq_setup(
> memchr_inv(hdr->reserved, 0, sizeof(hdr->reserved)))
> return -EINVAL;
>
> + if (hdr->flags & XFS_IREQ_SPECIAL) {
> + switch (hdr->ino) {
> + case XFS_IREQ_SPECIAL_ROOT:
> + hdr->ino = mp->m_sb.sb_rootino;
> + break;
> + default:
> + return -EINVAL;
> + }
> + }
> +
> if (XFS_INO_TO_AGNO(mp, hdr->ino) >= mp->m_sb.sb_agcount)
> return -EINVAL;
>
