linux-kernel - Re: [PATCH 4/4] iomap: don't abandon the whole copy when we have iomap_folio

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Message-ID: <dhjvmhfpmyf5ncbutlev6mmtgxatnuorfiv7i4q55wpzl7jrvn@asxbr2hv3xfv>
Date: Mon, 15 Sep 2025 12:50:54 +0200
From: "Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>
To: alexjlzheng@...il.com
Cc: hch@...radead.org, brauner@...nel.org, djwong@...nel.org, 
	yi.zhang@...wei.com, linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Jinliang Zheng <alexjlzheng@...cent.com>
Subject: Re: [PATCH 4/4] iomap: don't abandon the whole copy when we have
 iomap_folio_state

> +static int iomap_trim_tail_partial(struct inode *inode, loff_t pos,
> +		size_t copied, struct folio *folio)
> +{
> +	struct iomap_folio_state *ifs = folio->private;
> +	unsigned block_size, last_blk, last_blk_bytes;
> +
> +	if (!ifs || !copied)
> +		return 0;
> +
> +	block_size = 1 << inode->i_blkbits;
> +	last_blk = offset_in_folio(folio, pos + copied - 1) >> inode->i_blkbits;
> +	last_blk_bytes = (pos + copied) & (block_size - 1);
> +
> +	if (!ifs_block_is_uptodate(ifs, last_blk))
> +		copied -= min(copied, last_blk_bytes);

If pos is aligned to block_size, is there a scenario where 
copied < last_blk_bytes?

Trying to understand why you are using a min() here.
--
Pankaj