linux-kernel - Re: [PATCH v2 20/46] mm/migrate: Add folio_migrate

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Message-ID: <YNlrsfsk/dziia2q@infradead.org>
Date:   Mon, 28 Jun 2021 07:26:57 +0100
From:   Christoph Hellwig <hch@...radead.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Christoph Hellwig <hch@...radead.org>, akpm@...ux-foundation.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 20/46] mm/migrate: Add folio_migrate_copy()

On Thu, Jun 24, 2021 at 07:02:23PM +0100, Matthew Wilcox wrote:
> > What is the advantage of copying backwards here to start with?
> 
> Easier to write the loop this way?  I suppose we could do it as ...
> 
> 	unsigned int i, nr = folio_nr_pages(folio);
> 
> 	for (i = 0; i < nr; i++) {
> 		/* folio_page() handles discontinuities in memmap */
> 		copy_highpage(folio_page(newfolio, i), folio_page(folio, i));
> 		cond_resched();
> 	}

I'd prefer that if there is no obvious downside.