linux-ext4 - Re: [RFC PATCH v4 27/34] ext4: implement zero

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Message-ID: <ZjIN9nuV6SaNODfE@dread.disaster.area>
Date: Wed, 1 May 2024 19:40:06 +1000
From: Dave Chinner <david@...morbit.com>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, tytso@....edu,
	adilger.kernel@...ger.ca, jack@...e.cz, ritesh.list@...il.com,
	hch@...radead.org, djwong@...nel.org, willy@...radead.org,
	zokeefe@...gle.com, yi.zhang@...wei.com, chengzhihao1@...wei.com,
	yukuai3@...wei.com, wangkefeng.wang@...wei.com
Subject: Re: [RFC PATCH v4 27/34] ext4: implement zero_range iomap path

On Wed, Apr 10, 2024 at 10:29:41PM +0800, Zhang Yi wrote:
> From: Zhang Yi <yi.zhang@...wei.com>
> 
> Add ext4_iomap_zero_range() for the zero_range iomap path, it zero out
> the mapped blocks, all work have been done in iomap_zero_range(), so
> call it directly.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
> ---
>  fs/ext4/inode.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 9d694c780007..5af3b8acf1b9 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4144,6 +4144,13 @@ static int __ext4_block_zero_page_range(handle_t *handle,
>  	return err;
>  }
>  
> +static int ext4_iomap_zero_range(struct inode *inode,
> +				 loff_t from, loff_t length)
> +{
> +	return iomap_zero_range(inode, from, length, NULL,
> +				&ext4_iomap_buffered_read_ops);
> +}

Zeroing is a buffered write operation, not a buffered read
operation. It runs though iomap_write_begin(), so needs all the
stale iomap detection stuff to be set up for correct operation.

-Dave.
-- 
Dave Chinner
david@...morbit.com