From: Jaewon Kim <jaewon31.kim@samsung.com>
To: Michal Hocko <mhocko@suse.com>
Cc: "jstultz@google.com" <jstultz@google.com>,
"tjmercier@google.com" <tjmercier@google.com>,
"sumit.semwal@linaro.org" <sumit.semwal@linaro.org>,
"daniel.vetter@ffwll.ch" <daniel.vetter@ffwll.ch>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"hannes@cmpxchg.org" <hannes@cmpxchg.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"jaewon31.kim@gmail.com" <jaewon31.kim@gmail.com>
Subject: RE: [PATCH v3] dma-buf/heaps: system_heap: avoid too much allocation
Date: Wed, 12 Apr 2023 18:44:40 +0900 [thread overview]
Message-ID: <20230412094440epcms1p445319579ead0d0576bb616ebb07501b4@epcms1p4> (raw)
In-Reply-To: <ZDZ4j7UdBt32j28J@dhcp22.suse.cz>
>On Wed 12-04-23 17:57:26, Jaewon Kim wrote:
>> >Sorry for being late. I know there was some pre-existing discussion
>> >around that but I didn't have time to participate.
>> >
>> >On Mon 10-04-23 16:32:28, Jaewon Kim wrote:
>> >> @@ -350,6 +350,9 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
>> >> struct page *page, *tmp_page;
>> >> int i, ret = -ENOMEM;
>> >>
>> >> + if (len / PAGE_SIZE > totalram_pages())
>> >> + return ERR_PTR(-ENOMEM);
>> >> +
>> >
>> >This is an antipattern imho. Check 7661809d493b ("mm: don't allow
>> >oversized kvmalloc() calls") how kvmalloc has dealt with a similar
>>
>> Hello Thank you for the information.
>>
>> I tried to search the macro of INT_MAX.
>>
>> include/vdso/limits.h
>> #define INT_MAX ((int)(~0U >> 1))
>>
>> AFAIK the dma-buf system heap user can request that huge size more than 2GB.
>
>Do you have any pointers? This all is unreclaimable memory, right? How
>are those users constrained to not go overboard?
Correct dma-buf system heap memory is unreclaimable. To avoid that huge request,
this patch includes __GFP_RETRY_MAYFAIL.
#define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO | __GFP_RETRY_MAYFAIL)
>
>> So
>> I think totalram_pages() is better than INT_MAX in this case.
>>
>> >issue. totalram_pages doesn't really tell you anything about incorrect
>> >users. You might be on a low memory system where the request size is
>> >sane normally, it just doesn't fit into memory on that particular
>> >machine.
>>
>> Sorry maybe I'm not fully understand what you meant. User may requested
>> a huge size like 3GB on 2GB ram device. But I think that should be rejected
>> because it is bigger than the device ram size.
>
>Even totalram_pages/10 can be just unfeasible amount of data to be
>allocated without a major disruption. totalram_pages is no measure of
>the memory availability.
>If you want to have a ballpark estimation then si_mem_available might be
>something you are looking for. But I thought the sole purpose of this
>patch is to catch obviously buggy callers (like sign overflow lenght
>etc) rather than any memory consumption sanity check.
Yes if we want to avoid some big size, si_mem_available could be one option.
Actually I tried to do totalram_pages() / 2 like the old ion system heap in
the previous patch version. Anyway totalram_pages in this patch is used to
avoid the buggy size.
And as we discussed in v2 patch, __GFP_RETRY_MAYFAIL was added. And I think
the gfp makes us feel better in memory perspective.
>
>--
>Michal Hocko
>SUSE Labs
next prev parent reply other threads:[~2023-04-12 9:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20230410073304epcas1p4cf3079b096994d69472b7801bd530bc7@epcas1p4.samsung.com>
2023-04-10 7:32 ` [PATCH v3] dma-buf/heaps: system_heap: avoid too much allocation Jaewon Kim
2023-04-12 8:22 ` Michal Hocko
[not found] ` <CGME20230410073304epcas1p4cf3079b096994d69472b7801bd530bc7@epcms1p7>
2023-04-12 8:57 ` Jaewon Kim
2023-04-12 9:23 ` Michal Hocko
[not found] ` <CGME20230410073304epcas1p4cf3079b096994d69472b7801bd530bc7@epcms1p4>
2023-04-12 9:44 ` Jaewon Kim [this message]
2023-04-12 11:02 ` Michal Hocko
[not found] ` <CGME20230410073304epcas1p4cf3079b096994d69472b7801bd530bc7@epcms1p8>
2023-04-12 11:37 ` Jaewon Kim
2023-04-12 11:51 ` Michal Hocko
[not found] ` <CGME20230410073304epcas1p4cf3079b096994d69472b7801bd530bc7@epcms1p2>
2023-04-12 12:35 ` Jaewon Kim
2023-04-12 13:01 ` Michal Hocko
2023-04-12 16:49 ` T.J. Mercier
2023-04-12 22:10 ` Jaewon Kim
[not found] ` <CGME20230410073304epcas1p4cf3079b096994d69472b7801bd530bc7@epcms1p6>
2023-04-13 0:16 ` Jaewon Kim
2023-04-13 6:55 ` Michal Hocko
[not found] ` <CGME20230410073304epcas1p4cf3079b096994d69472b7801bd530bc7@epcms1p1>
2023-04-13 7:01 ` Jaewon Kim
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