Re: [PATCH 1/2] xfs: track the number of blocks in each buftarg

[Dave Chinner <david@fromorbit.com>]

On Mon, Aug 25, 2025 at 01:19:35PM +0200, Christoph Hellwig wrote:
> Add a bt_nr_blocks to track the number of blocks in each buftarg, and
> replace the check that hard codes sb_dblock in xfs_buf_map_verify with
> this new value so that it is correct for non-ddev buftargs.  The
> RT buftarg only has a superblock in the first block, so it is unlikely
> to trigger this, or are we likely to ever have enough blocks in the
> in-memory buftargs, but we might as well get the check right.
> 
> Fixes: 10616b806d1d ("xfs: fix _xfs_buf_find oops on blocks beyond the filesystem end")
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_buf.c              | 38 +++++++++++++++++++----------------
>  fs/xfs/xfs_buf.h              |  4 +++-
>  fs/xfs/xfs_buf_item_recover.c |  7 +++++++
>  fs/xfs/xfs_super.c            |  7 ++++---
>  fs/xfs/xfs_trans.c            | 21 +++++++++----------
>  5 files changed, 45 insertions(+), 32 deletions(-)
....

> diff --git a/fs/xfs/xfs_buf_item_recover.c b/fs/xfs/xfs_buf_item_recover.c
> index 5d58e2ae4972..d43234e04174 100644
> --- a/fs/xfs/xfs_buf_item_recover.c
> +++ b/fs/xfs/xfs_buf_item_recover.c
> @@ -736,6 +736,13 @@ xlog_recover_do_primary_sb_buffer(
>  	 */
>  	xfs_sb_from_disk(&mp->m_sb, dsb);
>  
> +	/*
> +	 * Grow can change the device size.  Mirror that into the buftarg.
> +	 */
> +	mp->m_ddev_targp->bt_nr_blocks = mp->m_sb.sb_dblocks;
> +	if (mp->m_rtdev_targp && mp->m_rtdev_targp != mp->m_ddev_targp)
> +		mp->m_rtdev_targp->bt_nr_blocks = mp->m_sb.sb_dblocks;
                                                              ^
That's not right.

Perhaps we need some growfs crash/recovery tests to exercise this
code....

-Dave.
-- 
Dave Chinner
david@fromorbit.com