Re: [PATCHv9 6/6] iomap: Add per-block dirty state tracking to improve performance

[Christoph Hellwig <hch@infradead.org>]

Just some nitpicks, this otherwise looks fine.

First during the last patches ifs as a variable name has started
to really annoy me and I'm not sure why.  I'd like to hear from the
others, bu maybe just state might be a better name that flows easier?

> +static void iomap_clear_range_dirty(struct folio *folio, size_t off, size_t len)
> +{
> +	struct iomap_folio_state *ifs = iomap_get_ifs(folio);
> +
> +	if (!ifs)
> +		return;
> +	iomap_ifs_clear_range_dirty(folio, ifs, off, len);

Maybe just do

	if (ifs)
		iomap_ifs_clear_range_dirty(folio, ifs, off, len);

?

But also do we even need the ifs argument to iomap_ifs_clear_range_dirty
after we've removed it everywhere else earlier?

> +	/*
> +	 * When we have per-block dirty tracking, there can be
> +	 * blocks within a folio which are marked uptodate
> +	 * but not dirty. In that case it is necessary to punch
> +	 * out such blocks to avoid leaking any delalloc blocks.
> +	 */
> +	ifs = iomap_get_ifs(folio);
> +	if (!ifs)
> +		goto skip_ifs_punch;
> +
> +	last_byte = min_t(loff_t, end_byte - 1,
> +		(folio_next_index(folio) << PAGE_SHIFT) - 1);
> +	first_blk = offset_in_folio(folio, start_byte) >> blkbits;
> +	last_blk = offset_in_folio(folio, last_byte) >> blkbits;
> +	for (i = first_blk; i <= last_blk; i++) {
> +		if (!iomap_ifs_is_block_dirty(folio, ifs, i)) {
> +			ret = punch(inode, folio_pos(folio) + (i << blkbits),
> +				    1 << blkbits);
> +			if (ret)
> +				goto out;
> +		}
> +	}
> +
> +skip_ifs_punch:

And happy to hear from the others, but to me having a helper for
all the iomap_folio_state manipulation rather than having it in
the middle of the function and jumped over if not needed would
improve the code structure.