linux-kernel - Re: [PATCH 0/2] Support direct I/O read and write for memory allocated by dmabuf

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Message-ID: <d70cf558-cf34-4909-a33e-58e3a10bbc0c@vivo.com>
Date: Wed, 10 Jul 2024 22:35:48 +0800
From: Lei Liu <liulei.rjpt@...o.com>
To: Christian König <christian.koenig@....com>,
 Sumit Semwal <sumit.semwal@...aro.org>,
 Benjamin Gaignard <benjamin.gaignard@...labora.com>,
 Brian Starkey <Brian.Starkey@....com>, John Stultz <jstultz@...gle.com>,
 "T.J. Mercier" <tjmercier@...gle.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>, Matthew Wilcox <willy@...radead.org>,
 Muhammad Usama Anjum <usama.anjum@...labora.com>,
 Andrei Vagin <avagin@...gle.com>, Ryan Roberts <ryan.roberts@....com>,
 Kefeng Wang <wangkefeng.wang@...wei.com>, linux-media@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
 linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 linux-mm@...ck.org, Daniel Vetter <daniel@...ll.ch>,
 "Vetter, Daniel" <daniel.vetter@...el.com>
Cc: opensource.kernel@...o.com
Subject: Re: [PATCH 0/2] Support direct I/O read and write for memory
 allocated by dmabuf

在 2024/7/10 22:14, Christian König 写道:
> Am 10.07.24 um 15:57 schrieb Lei Liu:
>> Use vm_insert_page to establish a mapping for the memory allocated
>> by dmabuf, thus supporting direct I/O read and write; and fix the
>> issue of incorrect memory statistics after mapping dmabuf memory.
>
> Well big NAK to that! Direct I/O is intentionally disabled on DMA-bufs.

Hello! Could you explain why direct_io is disabled on DMABUF? Is there 
any historical reason for this?

>
> We already discussed enforcing that in the DMA-buf framework and this 
> patch probably means that we should really do that.
>
> Regards,
> Christian.

Thank you for your response. With the application of AI large model 
edgeification, we urgently need support for direct_io on DMABUF to read 
some very large files. Do you have any new solutions or plans for this?

Regards,
Lei Liu.

>
>>
>> Lei Liu (2):
>>    mm: dmabuf_direct_io: Support direct_io for memory allocated by 
>> dmabuf
>>    mm: dmabuf_direct_io: Fix memory statistics error for dmabuf 
>> allocated
>>      memory with direct_io support
>>
>>   drivers/dma-buf/heaps/system_heap.c |  5 +++--
>>   fs/proc/task_mmu.c                  |  8 +++++++-
>>   include/linux/mm.h                  |  1 +
>>   mm/memory.c                         | 15 ++++++++++-----
>>   mm/rmap.c                           |  9 +++++----
>>   5 files changed, 26 insertions(+), 12 deletions(-)
>>
>