linux-kernel - Re: [RFC 0/1] Convert is_migrate_isolate_page() to is_migrate_isolate

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Message-ID: <aBpeR5E6XoneDcEj@casper.infradead.org>
Date: Tue, 6 May 2025 20:08:55 +0100
From: Matthew Wilcox <willy@...radead.org>
To: nifan.cxl@...il.com
Cc: muchun.song@...ux.dev, osalvador@...e.de, mcgrof@...nel.org,
	a.manzanares@...sung.com, dave@...olabs.net,
	akpm@...ux-foundation.org, david@...hat.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Fan Ni <fan.ni@...sung.com>
Subject: Re: [RFC 0/1] Convert is_migrate_isolate_page() to
 is_migrate_isolate_folio()

On Tue, May 06, 2025 at 11:38:28AM -0700, nifan.cxl@...il.com wrote:
> From: Fan Ni <fan.ni@...sung.com>
> 
> Sending out this patch per Matthew Wilcox's suggestion 
> that we need to convert is_migrate_isolate_page() to use folio
> https://lore.kernel.org/linux-mm/Z_XmUrbxKtYmzmJ6@casper.infradead.org/

That's not what I said!

This is what I said:
> >  
> > -		if (is_migrate_isolate_page(&folio->page))
> > +		if (is_migrate_isolate_page(folio_page(folio, 0)))
> >  			continue;
>
> I think we need an is_migrate_isolate_folio() instead of this.

> However, when looking into the code, I have noticed that among the uers
> of is_migrate_isolate_page(), in most cases the page passed in is from a 
> a pageblock. 
> I am not sure how we should proceed with these cases.
> Should we deal with pageblock or just leave it as it is and only do the page
> to folio conversion for the pages within?

Neither.  Add a folio_test_migrate_isolate() in addition to
is_migrate_isolate_page().  Don't force a conversion as it's a
legitimate question to ask of pages as well as of folios.
And some of the pages you want to ask it of may well not be part of
folios (they may be part of a slab or some other memdesc).