From: Nicholas Piggin <npiggin@gmail•com>
To: Matthew Wilcox <willy@infradead•org>
Cc: linux-arch@vger•kernel.org, Will Deacon <will@kernel•org>,
Catalin Marinas <catalin.marinas@arm•com>,
x86@kernel•org, linux-kernel@vger•kernel.org, linux-mm@kvack•org,
Ingo Molnar <mingo@redhat•com>, Borislav Petkov <bp@alien8•de>,
"H. Peter Anvin" <hpa@zytor•com>,
Thomas Gleixner <tglx@linutronix•de>,
linuxppc-dev@lists•ozlabs.org,
linux-arm-kernel@lists•infradead.org
Subject: Re: [PATCH v2 1/4] mm/vmalloc: fix vmalloc_to_page for huge vmap mappings
Date: Tue, 14 Apr 2020 21:31:49 +1000 [thread overview]
Message-ID: <1586863573.ufpx8o7f0i.astroid@bobo.none> (raw)
In-Reply-To: <20200413133444.GM21484@bombadil.infradead.org>
Excerpts from Matthew Wilcox's message of April 13, 2020 11:34 pm:
> On Mon, Apr 13, 2020 at 10:53:00PM +1000, Nicholas Piggin wrote:
>> vmalloc_to_page returns NULL for addresses mapped by larger pages[*].
>> Whether or not a vmap is huge depends on the architecture details,
>> alignments, boot options, etc., which the caller can not be expected
>> to know. Therefore HUGE_VMAP is a regression for vmalloc_to_page.
>>
>> This change teaches vmalloc_to_page about larger pages, and returns
>> the struct page that corresponds to the offset within the large page.
>> This makes the API agnostic to mapping implementation details.
>
> I'm trying to get us away from returning tail pages from various
> functions. How much of a pain would it be to return the head page
> instead of the tail page?
Well, this is a fix for the interface for HUGE_VMAP stuff so it
doesn't really make sense to change the implementation here. If you
want to change or make a different API that would be a later patch, no?
> Obviously the implementation gets simpler,
> but can the callers cope? I've been focusing on the page cache, so I
> haven't been looking at the vmalloc side of things at all.
Well callers that operate on ioremap today (and vmalloc tomorrow) won't
cope, because they're expecting a base page. If you wanted to change it
I suspect the way to go would be introduce a new function and move
everyone over individually.
Thanks,
Nick
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next prev parent reply other threads:[~2020-04-14 11:33 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-13 12:52 [PATCH v2 0/4] huge vmalloc mappings Nicholas Piggin
2020-04-13 12:53 ` [PATCH v2 1/4] mm/vmalloc: fix vmalloc_to_page for huge vmap mappings Nicholas Piggin
2020-04-13 13:34 ` Matthew Wilcox
2020-04-14 11:31 ` Nicholas Piggin [this message]
2020-04-13 12:53 ` [PATCH v2 2/4] mm: Move ioremap page table mapping function to mm/ Nicholas Piggin
2020-04-13 12:53 ` [PATCH v2 3/4] mm: HUGE_VMAP arch query functions cleanup Nicholas Piggin
2020-04-13 12:53 ` [PATCH v2 4/4] mm/vmalloc: Hugepage vmalloc mappings Nicholas Piggin
2020-04-13 13:41 ` Matthew Wilcox
2020-04-14 11:39 ` Nicholas Piggin
2020-04-14 12:28 ` Christophe Leroy
2020-04-14 14:20 ` Matthew Wilcox
2020-04-14 7:23 ` Christoph Hellwig
2020-04-14 12:13 ` Nicholas Piggin
2020-04-14 13:02 ` Christoph Hellwig
2020-04-14 14:48 ` Nicholas Piggin
2020-04-15 10:47 ` Will Deacon
2020-04-16 2:38 ` Nicholas Piggin
2020-07-01 7:10 ` Zefan Li
2020-07-03 0:15 ` Nicholas Piggin
2020-07-20 2:02 ` Zefan Li
2020-07-20 2:49 ` Nicholas Piggin
2020-04-14 0:27 ` [PATCH v2 0/4] huge " David Rientjes
2020-04-14 12:23 ` Nicholas Piggin
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