From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 0EF8D3FD96E for ; Wed, 30 Sep 2026 10:17:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790763469; cv=none; b=rMVF0LveGsQqDpWB95Uk4rO5jjy82/i8DUEEe6HtfY1NR5jX+FndJ3ifUCdqHisqmS5j+Yr6yEmMh6YBGIfRqmGYmlhG0hN/gG+uTPhC00ab2GZWz5pxtdr20wWFoNjJqZ4f+gNJvCh+hQxF18+BV2XB2xLF6i1fhGbpjqVkKeE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790763469; c=relaxed/simple; bh=BwGIIN541zdHe/E+krLKu5TOuGQI4YuwnQzCjPMtyXo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=SXvGWHCKx613WrL/uVm73jRJ6tsig6UCEfjaQlA2CEXIzf9puK9PRL7cGUBmYIucTosMJfdtk3HJcHgu8DvpRN70lavJeALHH+1c53RlFwwWkd+1AbSIBmOciQ5zEIWtt+ViqQ7WcBva5V+EtzOHlpuJHnX3sb/JLTRTnCtOrUg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DMeCpVFj; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DMeCpVFj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE54B1F00893; Wed, 30 Sep 2026 10:17:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790763467; bh=W3cgkYtIbNvYvCR/75csc07cJMiX3SGtqX5E3pPjB2I=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=DMeCpVFj6xuNgEpmQg1zia+EB1nBbXPjHKzpR/UVERO+nuN4wz1pK6tE6NrS4O8Ih JfifjGq3V22BCCMwlaKeT5qR8qcjcPTOBwAnG5gJd5pFFTo/PMNfDaAfHYakuPuik4 cvBCW8mWhdMYvczzkeV0FwJun2IT4KRtP/XVOmUiFPeyFOljLR9fgpZ3+VQHI2ERGd Cmpfax8Osj15CK1XcutgwE3EyDcv8gYKbDh3g9e9bHJke6UY8A2G9s3yC8oN9r1UW8 2X3HGF6OkTpp6cpnM7iCyHu/jn8z1cy/cgOVy8KeZkW+VRrAe9kQyUT/f0K6fszUXE nEYJfpVzXjxww== Message-ID: Date: Wed, 30 Sep 2026 12:17:43 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 00/15] mm: eliminate &folio->page references in mm/ To: Nilay Vaish , Andrew Morton Cc: Matthew Wilcox , Greg Thelen , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260929215206.516490-1-nilayvaish@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/29/26 23:51, Nilay Vaish wrote: > As part of the memdescs effort to separate struct folio from struct page > and allocate struct folio dynamically [1], struct folio will no longer > embed a struct page member (folio->page), and the address of a struct > folio will no longer equal the address of its head struct page in > vmemmap. > > This series eliminates all but one of the remaining &folio->page > references across mm/*.c (25 files) by converting them to: I recall that Willy mentioned at some point that when changing this we actually have to think about what the right thing to do is. As &folio->page can serve as a reminder that something needs a proper solution instead of a mechanical change. So while folio_page(folio, 0) is the mechanical change, a much more often we'll have to ask us what the actual future-proof thing is. For example: diff --git a/mm/migrate.c b/mm/migrate.c index 7bdcdb57652f..b027c938d830 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -266,8 +266,8 @@ void putback_movable_pages(struct list_head *l) continue; } list_del(&folio->lru); - if (unlikely(page_has_movable_ops(&folio->page))) { - putback_movable_ops_page(&folio->page); + if (unlikely(page_has_movable_ops(folio_page(folio, 0)))) { + putback_movable_ops_page(folio_page(folio, 0)); } else { node_stat_mod_folio(folio, NR_ISOLATED_ANON + folio_is_file_lru(folio), -folio_nr_pages(folio)); Is stupid. These things won't be folios in the future, so we actually *want to keep* using &folio->page here as a reminder that this really must be reworked entirely differently. Which makes this rather hard to review and makes me wonder whether core maintainers should actually drive such a cleanup. Unless Willy explicitly asked you to do that work, of course. -- Cheers, David