linux-ext4 - Re: [PATCHv2 1/2] iomap: Fix iomap_adjust_read

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Date: Thu, 9 May 2024 12:33:01 +0200
From: Jan Kara <jack@...e.cz>
To: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
Cc: linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
	"Darrick J . Wong" <djwong@...nel.org>,
	Ojaswin Mujoo <ojaswin@...ux.ibm.com>, Jan Kara <jack@...e.cz>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCHv2 1/2] iomap: Fix iomap_adjust_read_range for plen
 calculation

On Tue 07-05-24 14:25:42, Ritesh Harjani (IBM) wrote:
> If the extent spans the block that contains i_size, we need to handle
> both halves separately so that we properly zero data in the page cache
> for blocks that are entirely outside of i_size. But this is needed only
> when i_size is within the current folio under processing.
> "orig_pos + length > isize" can be true for all folios if the mapped
> extent length is greater than the folio size. That is making plen to
> break for every folio instead of only the last folio.
> 
> So use orig_plen for checking if "orig_pos + orig_plen > isize".
> 
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
> cc: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Darrick J. Wong <djwong@...nel.org>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza


> ---
>  fs/iomap/buffered-io.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 4e8e41c8b3c0..9f79c82d1f73 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -241,6 +241,7 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
>  	unsigned block_size = (1 << block_bits);
>  	size_t poff = offset_in_folio(folio, *pos);
>  	size_t plen = min_t(loff_t, folio_size(folio) - poff, length);
> +	size_t orig_plen = plen;
>  	unsigned first = poff >> block_bits;
>  	unsigned last = (poff + plen - 1) >> block_bits;
> 
> @@ -277,7 +278,7 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
>  	 * handle both halves separately so that we properly zero data in the
>  	 * page cache for blocks that are entirely outside of i_size.
>  	 */
> -	if (orig_pos <= isize && orig_pos + length > isize) {
> +	if (orig_pos <= isize && orig_pos + orig_plen > isize) {
>  		unsigned end = offset_in_folio(folio, isize - 1) >> block_bits;
> 
>  		if (first <= end && last > end)
> --
> 2.44.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR