Re: [PATCH 4/6] xfs: call xfs_flush_unmap_range from xfs_free_file_space

[Dave Chinner <david@fromorbit.com>]

On Tue, Aug 27, 2024 at 08:50:48AM +0200, Christoph Hellwig wrote:
> Call xfs_flush_unmap_range from xfs_free_file_space so that
> xfs_file_fallocate doesn't have to predict which mode will call it.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_bmap_util.c |  8 ++++++++
>  fs/xfs/xfs_file.c      | 21 ---------------------
>  2 files changed, 8 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index fe2e2c93097550..187a0dbda24fc4 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -848,6 +848,14 @@ xfs_free_file_space(
>  	if (len <= 0)	/* if nothing being freed */
>  		return 0;
>  
> +	/*
> +	 * Now AIO and DIO has drained we flush and (if necessary) invalidate
> +	 * the cached range over the first operation we are about to run.
> +	 */
> +	error = xfs_flush_unmap_range(ip, offset, len);
> +	if (error)
> +		return error;
> +
>  	startoffset_fsb = XFS_B_TO_FSB(mp, offset);
>  	endoffset_fsb = XFS_B_TO_FSBT(mp, offset + len);

Ok, so if we ever change the zeroing implementation to not punch a
hole first, we're going to have to make sure we add this to whatever
new zeroing implementation we have.

Can you leave a comment in the FALLOC_FL_ZERO_RANGE implementation
code that notes it currently relies on the xfs_flush_unmap_range()
in xfs_free_file_space() for correct operation?

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