linux-kernel - Re: [PATCH v5 1/4] iomap: make sure iomap_adjust_read_range() are aligned with block

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Message-ID: <aNWRHkLos9bM8a_8@bfoster>
Date: Thu, 25 Sep 2025 14:59:42 -0400
From: Brian Foster <bfoster@...hat.com>
To: alexjlzheng@...il.com
Cc: brauner@...nel.org, djwong@...nel.org, hch@...radead.org,
	kernel@...kajraghav.com, linux-xfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	yi.zhang@...wei.com, Jinliang Zheng <alexjlzheng@...cent.com>
Subject: Re: [PATCH v5 1/4] iomap: make sure iomap_adjust_read_range() are
 aligned with block_size

On Tue, Sep 23, 2025 at 12:21:55PM +0800, alexjlzheng@...il.com wrote:
> From: Jinliang Zheng <alexjlzheng@...cent.com>
> 
> iomap_folio_state marks the uptodate state in units of block_size, so
> it is better to check that pos and length are aligned with block_size.
> 
> Signed-off-by: Jinliang Zheng <alexjlzheng@...cent.com>
> ---
>  fs/iomap/buffered-io.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index fd827398afd2..ee1b2cd8a4b4 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -234,6 +234,9 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
>  	unsigned first = poff >> block_bits;
>  	unsigned last = (poff + plen - 1) >> block_bits;
>  
> +	WARN_ON_ONCE(*pos & (block_size - 1));
> +	WARN_ON_ONCE(length & (block_size - 1));
> +

I thought Joanne's patch [1] enhanced this function to deal with this
sort of corner case. Is this necessary if we go that route or am I
missing something?

Brian

[1] https://lore.kernel.org/linux-fsdevel/20250922180042.1775241-1-joannelkoong@gmail.com/

>  	/*
>  	 * If the block size is smaller than the page size, we need to check the
>  	 * per-block uptodate status and adjust the offset and length if needed
> -- 
> 2.49.0
> 
>