linux-ext4 - Re: [PATCH 4/6] xfs: call xfs_flush_unmap_range from xfs_free_file

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Message-ID: <Zs/lA5FJoF0Zd9Ip@dread.disaster.area>
Date: Thu, 29 Aug 2024 13:03:31 +1000
From: Dave Chinner <david@...morbit.com>
To: Christoph Hellwig <hch@....de>
Cc: Christian Brauner <brauner@...nel.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Chandan Babu R <chandan.babu@...cle.com>,
	Brian Foster <bfoster@...hat.com>, Jens Axboe <axboe@...nel.dk>,
	Jan Kara <jack@...e.cz>, "Darrick J. Wong" <djwong@...nel.org>,
	Theodore Ts'o <tytso@....edu>, linux-block@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-xfs@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 4/6] xfs: call xfs_flush_unmap_range from
 xfs_free_file_space

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@....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@...morbit.com