Re: [RFC PATCH 02/11] rust: add `pages` module for handling page allocation

From: Matthew Wilcox <willy@infradead.org>
To: Andreas Hindborg <nmi@metaspace.dk>
Cc: "Jens Axboe" <axboe@kernel.dk>, "Christoph Hellwig" <hch@lst.de>,
	"Keith Busch" <kbusch@kernel.org>,
	"Damien Le Moal" <Damien.LeMoal@wdc.com>,
	"Hannes Reinecke" <hare@suse.de>,
	lsf-pc@lists.linux-foundation.org,
	rust-for-linux@vger.kernel.org, linux-block@vger.kernel.org,
	"Miguel Ojeda" <ojeda@kernel.org>,
	"Alex Gaynor" <alex.gaynor@gmail.com>,
	"Wedson Almeida Filho" <wedsonaf@gmail.com>,
	"Boqun Feng" <boqun.feng@gmail.com>,
	"Gary Guo" <gary@garyguo.net>,
	"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
	"Benno Lossin" <benno.lossin@proton.me>,
	"open list" <linux-kernel@vger.kernel.org>,
	gost.dev@samsung.com
Subject: Re: [RFC PATCH 02/11] rust: add `pages` module for handling page allocation
Date: Fri, 5 May 2023 06:29:19 +0100	[thread overview]
Message-ID: <ZFSUL41P5t1NQPes@casper.infradead.org> (raw)
In-Reply-To: <871qjvtmb5.fsf@metaspace.dk>

On Fri, May 05, 2023 at 06:42:02AM +0200, Andreas Hindborg wrote:
> 
> Matthew Wilcox <willy@infradead.org> writes:
> 
> > On Wed, May 03, 2023 at 11:06:59AM +0200, Andreas Hindborg wrote:
> >> From: Andreas Hindborg <a.hindborg@samsung.com>
> >> 
> >> This patch adds support for working with pages of order 0. Support for pages
> >> with higher order is deferred. Page allocation flags are fixed in this patch.
> >> Future work might allow the user to specify allocation flags.
> >> 
> >> This patch is a heavily modified version of code available in the rust tree [1],
> >> primarily adding support for multiple page mapping strategies.
> >
> > This also seems misaligned with the direction of Linux development.
> > Folios are the future, pages are legacy.  Please, ask about what's
> > going on before wasting time on the past.
> 
> I see, thanks for the heads up! In this case I wanted to do an
> apples-apples comparison to the C null_blk driver. Since that is using
> kmap I wanted to have that. But let's bind to the folio_* APIs in the
> future, that would make sense.

Well, kmap() is essentially a no-op on 64-bit systems, so it's not
terribly relevant to doing a comparison.