Re: [PATCH 6/5 V2] iomap: readpages doesn't zero page tail beyond EOF properly

From: Christoph Hellwig <hch@infradead.org>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 6/5 V2] iomap: readpages doesn't zero page tail beyond EOF properly
Date: Wed, 21 Nov 2018 08:34:22 -0800	[thread overview]
Message-ID: <20181121163422.GB27540@infradead.org> (raw)
In-Reply-To: <20181121082736.GT19305@dastard>

On Wed, Nov 21, 2018 at 07:27:36PM +1100, Dave Chinner wrote:
> index d51e7a2ae641..b95110867eee 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -142,13 +142,14 @@ static void
>  iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
>  		loff_t *pos, loff_t length, unsigned *offp, unsigned *lenp)
>  {
> +	loff_t orig_pos = *pos;
> +	loff_t isize = i_size_read(inode);
>  	unsigned block_bits = inode->i_blkbits;
>  	unsigned block_size = (1 << block_bits);
>  	unsigned poff = offset_in_page(*pos);
>  	unsigned plen = min_t(loff_t, PAGE_SIZE - poff, length);
>  	unsigned first = poff >> block_bits;
>  	unsigned last = (poff + plen - 1) >> block_bits;
> -	unsigned end = offset_in_page(i_size_read(inode)) >> block_bits;
>  
>  	/*
>  	 * If the block size is smaller than the page size we need to check the
> @@ -183,8 +184,11 @@ iomap_adjust_read_range(struct inode *inode, struct iomap_page *iop,
>  	 * handle both halves separately so that we properly zero data in the
>  	 * page cache for blocks that are entirely outside of i_size.
>  	 */
> -	if (first <= end && last > end)
> -		plen -= (last - end) * block_size;
> +	if (orig_pos <= isize && orig_pos + length > isize) {
> +		unsigned end = offset_in_page(isize - 1) >> block_bits;
> +		if (first <= end && last > end)
> +			plen -= (last - end) * block_size;

Please add an empty line afte the variable declaration.

Otherwise this looks good to me:

Reviewed-by: Christoph Hellwig <hch@lst.de>