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From: Nicholas Piggin <npiggin@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>,
	Christoph Hellwig <hch@infradead.org>,
	Jonathan Cameron <Jonathan.Cameron@Huawei.com>,
	linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
	Zefan Li <lizefan@huawei.com>
Subject: Re: [PATCH v6 01/12] mm/vmalloc: fix vmalloc_to_page for huge vmap mappings
Date: Sat, 22 Aug 2020 08:42:40 +1000	[thread overview]
Message-ID: <1598049375.u9pf1rciw6.astroid@bobo.none> (raw)
In-Reply-To: <20200821130757.289570e4bb491672087d3396@linux-foundation.org>

Excerpts from Andrew Morton's message of August 22, 2020 6:07 am:
> On Sat, 22 Aug 2020 01:12:05 +1000 Nicholas Piggin <npiggin@gmail.com> 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.
> 
> I assume this doesn't matter in current mainline?
> If wrong, then what are the user-visible effects and why no cc:stable?

I haven't heard any reports, but in theory it could cause a prolem. The
commit 029c54b095995 from the changelog was made to paper over it. But
that was fixed properly afterward I think by 737326aa510b.

Not sure of the user visible problems currently. I think generally you
wouldn't do vmalloc_to_page() on ioremap() memory, so maybe callilng it
a regression is a bit strong. _Technically_ a regression, maybe.

Thanks,
Nick

  reply	other threads:[~2020-08-21 22:42 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21 15:12 [PATCH v6 00/12] huge vmalloc mappings Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 01/12] mm/vmalloc: fix vmalloc_to_page for huge vmap mappings Nicholas Piggin
2020-08-21 20:07   ` Andrew Morton
2020-08-21 22:42     ` Nicholas Piggin [this message]
2020-08-21 15:12 ` [PATCH v6 02/12] mm: apply_to_pte_range warn and fail if a large pte is encountered Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 03/12] mm/vmalloc: rename vmap_*_range vmap_pages_*_range Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 04/12] mm/ioremap: rename ioremap_*_range to vmap_*_range Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 05/12] mm: HUGE_VMAP arch support cleanup Nicholas Piggin
2020-08-21 20:14   ` Andrew Morton
2020-08-21 22:45     ` Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 06/12] powerpc: inline huge vmap supported functions Nicholas Piggin
2020-08-21 20:15   ` Andrew Morton
2020-08-21 15:12 ` [PATCH v6 07/12] arm64: " Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 08/12] x86: " Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 09/12] mm: Move vmap_range from mm/ioremap.c to mm/vmalloc.c Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 10/12] mm/vmalloc: add vmap_range_noflush variant Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 11/12] mm/vmalloc: Hugepage vmalloc mappings Nicholas Piggin
2020-08-21 15:38   ` Eric Dumazet
2020-08-21 16:05     ` Nicholas Piggin
2020-08-21 15:12 ` [PATCH v6 12/12] powerpc/64s/radix: Enable huge " Nicholas Piggin

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