linux-kernel - Re: [PATCH] mm: remove redundant if overhead

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Message-ID: <ZuBtvW9TWCnHte4V@casper.infradead.org>
Date: Tue, 10 Sep 2024 17:03:09 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Zhiguo Jiang <justinjiang@...o.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, opensource.kernel@...o.com
Subject: Re: [PATCH] mm: remove redundant if overhead

On Tue, Sep 10, 2024 at 10:39:45PM +0800, Zhiguo Jiang wrote:
> Remove redundant if judgment overhead.

It's not redundant; it avoids dirtying the cacheline if the folio
is already marked as dirty.

>  bool noop_dirty_folio(struct address_space *mapping, struct folio *folio)
>  {
> -	if (!folio_test_dirty(folio))
> -		return !folio_test_set_dirty(folio);
> -	return false;
> +	return !folio_test_set_dirty(folio);
>  }