linux-kernel - Re: [PATCH RFC 08/29] mm/migrate: rename putback_movable_folio() to putback_movable_ops

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Message-ID: <aFMQ65hUoOoLaXms@casper.infradead.org>
Date: Wed, 18 Jun 2025 20:18:03 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Zi Yan <ziy@...dia.com>
Cc: David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-doc@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, virtualization@...ts.linux.dev,
	linux-fsdevel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
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	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
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	Harry Yoo <harry.yoo@...cle.com>,
	Qi Zheng <zhengqi.arch@...edance.com>,
	Shakeel Butt <shakeel.butt@...ux.dev>
Subject: Re: [PATCH RFC 08/29] mm/migrate: rename putback_movable_folio() to
 putback_movable_ops_page()

On Wed, Jun 18, 2025 at 03:10:10PM -0400, Zi Yan wrote:
> On 18 Jun 2025, at 13:39, David Hildenbrand wrote:
> > +	/*
> > +	 * TODO: these pages will not be folios in the future. All
> > +	 * folio dependencies will have to be removed.
> > +	 */
> > +	struct folio *folio = page_folio(page);
> > +
> > +	VM_WARN_ON_ONCE_PAGE(!PageIsolated(page), page);
> > +	folio_lock(folio);
> > +	/* If the page was released by it's owner, there is nothing to do. */
> > +	if (PageMovable(page))
> > +		page_movable_ops(page)->putback_page(page);
> > +	ClearPageIsolated(page);
> > +	folio_unlock(folio);
> > +	folio_put(folio);
> 
> Why not use page version of lock, unlock, and put? Especially you are
> thinking about not using folio for these pages. Just a question,
> I am OK with current patch.

That would reintroduce unnecessary calls to compound_head().