From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4D0A277F3A for ; Fri, 2 Feb 2024 09:22:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706865775; cv=none; b=amxqFc+K9NMsB1nznm66XjhkUUq4h1A7r2+rsGzka450yH8HjhCFA145dpPEk/hel7/9/NVWHx3bxqXgr1LjQrYjlgVYzln0LBhaSe0l8qOB1V1+J7ARHcnRZ3KnoF2PlxzTu/nhcNq9e2g2hIm4c7cCIBwh4iEgXkswoiSrxdM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706865775; c=relaxed/simple; bh=TdWS27s4EMNXFrh+FGof0R8zvZMI3ZS+Gn1BrxmQcWw=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=p63MuscgZyycvTm2xSpzuJBeGzLnGKSOrxHXhnF4Ig5PSOrBXrPpI+oYwxuD9p+xmA5Ws7CJRR/97tqykvUDIZdY8IuY7tjwqb++QnqlDvaaM4xZiDTY+XCJmyrEJWxGpgZUZRIHkzNPEr9I6VLUbQGxSA39VgPsZp8/39HZNYo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=HYUcO5Mp; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="HYUcO5Mp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E617BC433C7; Fri, 2 Feb 2024 09:22:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1706865775; bh=TdWS27s4EMNXFrh+FGof0R8zvZMI3ZS+Gn1BrxmQcWw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=HYUcO5MpMzN6wi5pD+JUCPWDtxPsRImIKOIoK99ULMG0OiEBghKnlWUB82bTpGfVJ Ql/+23VSVy0jOuAbM4o6v+q/9iPetGbCaDt1xF4MXjqNP1Kq8ndaGEnsrHdJDoK2mx /nLuyjHKyYDoD+XLFnBFUc0YyG9LlkeuCpZhv3rA= Date: Fri, 2 Feb 2024 01:22:51 -0800 From: Andrew Morton To: Zhiguo Jiang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, opensource.kernel@vivo.com Subject: Re: [PATCH v2] mm:vmscan: shrink skip folio mapped by an exiting task Message-Id: <20240202012251.1aa5afbfdf2f8b3a862bced3@linux-foundation.org> In-Reply-To: <20240131131244.1144-1-justinjiang@vivo.com> References: <20240131131244.1144-1-justinjiang@vivo.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 31 Jan 2024 21:12:44 +0800 Zhiguo Jiang wrote: > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -840,6 +840,13 @@ static bool folio_referenced_one(struct folio *folio, > int referenced = 0; > unsigned long start = address, ptes = 0; > > + /* Skip this folio if it's mapped by an exiting task */ > + if (unlikely(!atomic_read(&vma->vm_mm->mm_users)) || > + unlikely(test_bit(MMF_OOM_SKIP, &vma->vm_mm->flags))) { > + pra->referenced = -1; > + return false; > + } The code comment explains what the code does. This is, as usual, pretty obvious from reading the code! A better comment is one which explains *why* the code is doing what it does.