linux-kernel - Re: [PATCH v8 01/10] fs: Allow fine-grained control of folio sizes

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Message-ID: <ZogN12rTqp7qfLVY@casper.infradead.org>
Date: Fri, 5 Jul 2024 16:14:31 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Dave Chinner <david@...morbit.com>
Cc: Ryan Roberts <ryan.roberts@....com>,
	"Pankaj Raghav (Samsung)" <kernel@...kajraghav.com>,
	chandan.babu@...cle.com, djwong@...nel.org, brauner@...nel.org,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	yang@...amperecomputing.com, linux-mm@...ck.org,
	john.g.garry@...cle.com, linux-fsdevel@...r.kernel.org,
	hare@...e.de, p.raghav@...sung.com, mcgrof@...nel.org,
	gost.dev@...sung.com, cl@...amperecomputing.com,
	linux-xfs@...r.kernel.org, hch@....de, Zi Yan <zi.yan@...t.com>
Subject: Re: [PATCH v8 01/10] fs: Allow fine-grained control of folio sizes

On Fri, Jul 05, 2024 at 02:32:37PM +1000, Dave Chinner wrote:
> > If the device is
> > asking for a blocksize > PAGE_SIZE and CONFIG_TRANSPARENT_HUGEPAGE is
> > not set, you should also decline to mount the filesystem.
> 
> What does CONFIG_TRANSPARENT_HUGEPAGE have to do with filesystems
> being able to use large folios?

You can't have large folios without CONFIG_TRANSPARENT_HUGEPAGE.
There's a bunch of infrastructure that's gated behind that.  I used to say
"somebody should fix that up", but honestly the amount of work I'm willing
to do to support hobbyist architectures has decreased dramatically.
Any useful system has THP support.