linux-kernel - Re: [PATCH] mm/vmalloc: fix mischeck pfn valid in vmap

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Message-ID: <20250318084453.GB19274@lst.de>
Date: Tue, 18 Mar 2025 09:44:53 +0100
From: Christoph Hellwig <hch@....de>
To: Huan Yang <link@...o.com>
Cc: Christoph Hellwig <hch@....de>, akpm@...ux-foundation.org,
	bingbu.cao@...ux.intel.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, lorenzo.stoakes@...cle.com,
	opensource.kernel@...o.com, rppt@...nel.org, ryan.roberts@....com,
	urezki@...il.com, ziy@...dia.com, vivek.kasireddy@...el.com
Subject: Re: [PATCH] mm/vmalloc: fix mischeck pfn valid in vmap_pfns

On Tue, Mar 18, 2025 at 04:39:40PM +0800, Huan Yang wrote:
> A folio may be 2MB or more large 1GB, what if we only need a little, 1M or 512MB, can vmap based on folio can solve it?

Then you only map part of it by passing a length argument.  Note that
in general when you have these large folios you also don't have highmem,
so if you only map one of them, or part of one of them you don't actually
need vmap at all and can just use folio-address..

> Normally, can offer 4k-page based array map it. But consider HVO, can't. That's why wanto base on pfn.

Well, for any large folio using this 4k based page interface is
actually highly inefficient.  So let's fix that.  And my loop in
willy as Mr. Folio while you're at it.