From: Miaohe Lin <linmiaohe@huawei.com>
To: Vlastimil Babka <vbabka@suse.cz>, Matthew Wilcox <willy@infradead.org>
Cc: <akpm@linux-foundation.org>, <sfr@canb.auug.org.au>,
<peterz@infradead.org>, <mgorman@techsingularity.net>,
<linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 6/6] mm/page_alloc.c: avoid allocating highmem pages via alloc_pages_exact_nid()
Date: Wed, 1 Sep 2021 16:05:44 +0800 [thread overview]
Message-ID: <d3cc4289-c62d-49d2-ef55-85f3e5c2e588@huawei.com> (raw)
In-Reply-To: <cde527a6-36cf-8a01-16b9-41e950676e48@suse.cz>
On 2021/9/1 0:37, Vlastimil Babka wrote:
> On 8/31/21 03:56, Miaohe Lin wrote:
>> On 2021/8/30 22:24, Matthew Wilcox wrote:
>>> On Mon, Aug 30, 2021 at 10:10:51PM +0800, Miaohe Lin wrote:
>>>> Don't use with __GFP_HIGHMEM because page_address() cannot represent
>>>> highmem pages without kmap(). Newly allocated pages would leak as
>>>> page_address() will return NULL for highmem pages here. But It works
>>>> now because the only caller does not specify __GFP_HIGHMEM now.
>>>
>>> This is a misunderstanding of how alloc_pages_exact() /
>>> alloc_pages_exact_nid() work. You simply can't call them with
>>> GFP_HIGHMEM.
>>>
>>
>> Yep, they can't work with GFP_HIGHMEM. So IMO it might be better to
>> get rid of GFP_HIGHMEM explicitly or add a comment to clarify this
>> situation to avoid future misbehavior. But this may be a unnecessary
>> worry... Do you prefer to not change anything here?
>
> I agree with the suggestion below...
>
>> Many thanks.
>>
>>> If you really must change anything here,
>>> s/__GFP_COMP/(__GFP_COMP|__GFP_HIGHMEM)/g throughout both
>>> alloc_pages_exact() and alloc_pages_exact_nid().
>
> ... which means __GFP_HIGHMEM would be stripped and additionally there would
> be a warning.
>
Looks good for me. Will do. Many thanks!
> .
>
prev parent reply other threads:[~2021-09-01 8:05 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-30 14:10 [PATCH 0/6] Cleanups and fixup for page_alloc Miaohe Lin
2021-08-30 14:10 ` [PATCH 1/6] mm/page_alloc.c: remove meaningless VM_BUG_ON() in pindex_to_order() Miaohe Lin
2021-08-31 13:34 ` Mel Gorman
2021-08-31 14:05 ` David Hildenbrand
2021-08-30 14:10 ` [PATCH 2/6] mm/page_alloc.c: simplify the code by using macro K() Miaohe Lin
2021-08-31 8:54 ` Oleksandr Natalenko
2021-08-31 11:08 ` Miaohe Lin
2021-08-31 14:19 ` Oleksandr Natalenko
2021-09-01 7:37 ` Miaohe Lin
2021-09-01 7:46 ` Oleksandr Natalenko
2021-09-01 8:17 ` Miaohe Lin
2021-09-01 21:25 ` David Laight
2021-09-02 6:32 ` Miaohe Lin
2021-08-31 13:35 ` Mel Gorman
2021-08-31 14:07 ` David Hildenbrand
2021-08-30 14:10 ` [PATCH 3/6] mm/page_alloc.c: remove obsolete comment in free_pcppages_bulk() Miaohe Lin
2021-08-31 13:38 ` Mel Gorman
2021-09-01 7:49 ` Miaohe Lin
2021-09-01 15:14 ` Mel Gorman
2021-09-02 6:25 ` Miaohe Lin
2021-08-30 14:10 ` [PATCH 4/6] mm/page_alloc.c: use helper function zone_spans_pfn() Miaohe Lin
2021-08-31 13:39 ` Mel Gorman
2021-08-31 14:08 ` David Hildenbrand
2021-08-30 14:10 ` [PATCH 5/6] mm/page_alloc.c: avoid accessing uninitialized pcp page migratetype Miaohe Lin
2021-08-31 13:43 ` Mel Gorman
2021-08-31 14:23 ` David Hildenbrand
2021-09-01 8:02 ` Miaohe Lin
2021-09-01 8:10 ` David Hildenbrand
2021-09-01 8:18 ` Miaohe Lin
2021-08-31 16:34 ` Vlastimil Babka
2021-09-01 8:04 ` Miaohe Lin
2021-08-30 14:10 ` [PATCH 6/6] mm/page_alloc.c: avoid allocating highmem pages via alloc_pages_exact_nid() Miaohe Lin
2021-08-30 14:24 ` Matthew Wilcox
2021-08-31 1:56 ` Miaohe Lin
2021-08-31 16:37 ` Vlastimil Babka
2021-09-01 8:05 ` Miaohe Lin [this message]
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