From: Matthew Wilcox <willy@infradead.org>
To: Huang Shijie <sjhuang@iluvatar.ai>
Cc: akpm@linux-foundation.org, william.kucharski@oracle.com,
ira.weiny@intel.com, palmer@sifive.com, axboe@kernel.dk,
keescook@chromium.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm/gup.c: fix the wrong comments
Date: Mon, 8 Apr 2019 07:13:13 -0700 [thread overview]
Message-ID: <20190408141313.GU22763@bombadil.infradead.org> (raw)
In-Reply-To: <20190408023746.16916-1-sjhuang@iluvatar.ai>
On Mon, Apr 08, 2019 at 10:37:45AM +0800, Huang Shijie wrote:
> When CONFIG_HAVE_GENERIC_GUP is defined, the kernel will use its own
> get_user_pages_fast().
>
> In the following scenario, we will may meet the bug in the DMA case:
> .....................
> get_user_pages_fast(start,,, pages);
> ......
> sg_alloc_table_from_pages(, pages, ...);
> .....................
>
> The root cause is that sg_alloc_table_from_pages() requires the
> page order to keep the same as it used in the user space, but
> get_user_pages_fast() will mess it up.
I don't understand how get_user_pages_fast() can return the pages in a
different order in the array from the order they appear in userspace.
Can you explain?
next prev parent reply other threads:[~2019-04-08 14:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-08 2:37 [PATCH 1/2] mm/gup.c: fix the wrong comments Huang Shijie
2019-04-08 2:37 ` [PATCH 2/2] lib/scatterlist.c: add more commit for sg_alloc_table_from_pages Huang Shijie
2019-04-08 14:13 ` Matthew Wilcox [this message]
2019-04-09 1:08 ` [PATCH 1/2] mm/gup.c: fix the wrong comments Huang Shijie
2019-04-09 2:49 ` Matthew Wilcox
2019-04-09 3:04 ` Huang Shijie
2019-04-09 11:19 ` Matthew Wilcox
2019-04-09 14:55 ` Weiny, Ira
2019-04-10 1:20 ` Huang Shijie
2019-04-10 18:04 ` Ira Weiny
2019-04-09 20:23 ` Ira Weiny
2019-04-10 1:18 ` Huang Shijie
2019-04-10 18:08 ` Ira Weiny
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