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Date:   Fri, 28 Oct 2022 13:42:54 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc:     linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Christoph Hellwig <hch@infradead.org>,
        "Darrick J . Wong" <djwong@kernel.org>,
        Aravinda Herle <araherle@in.ibm.com>
Subject: Re: [RFC 2/2] iomap: Support subpage size dirty tracking to improve
 write performance
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References: <cover.1666928993.git.ritesh.list@gmail.com>
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On Fri, Oct 28, 2022 at 10:00:33AM +0530, Ritesh Harjani (IBM) wrote:
> @@ -1354,7 +1399,8 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
>  	 * invalid, grab a new one.
>  	 */
>  	for (i = 0; i < nblocks && pos < end_pos; i++, pos += len) {
> -		if (iop && !test_bit(i, iop->state))
> +		if (iop && (!test_bit(i, iop->state) ||
> +			    !test_bit(i + nblocks, iop->state)))
>  			continue;
>  
>  		error = wpc->ops->map_blocks(wpc, inode, pos);

Why do we need to test both uptodate and dirty?  Surely we only need to
test the dirty bit?  How can a !uptodate block ever be marked as dirty?

More generally, I think open-coding this is going to lead to confusion.
We need wrappers like 'iop_block_dirty()' and 'iop_block_uptodate()'.
(iop is still a bad name for this, but nobody's stepped up with a better
one yet).