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Content-Type: text/plain
From:   Huang Shijie <sjhuang@iluvatar.ai>
To:     <akpm@linux-foundation.org>
CC:     <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>,
        Huang Shijie <sjhuang@iluvatar.ai>
Subject: [PATCH 2/2] lib/scatterlist.c: add more commit for sg_alloc_table_from_pages
Date:   Mon, 8 Apr 2019 10:37:46 +0800
Message-ID: <20190408023746.16916-2-sjhuang@iluvatar.ai>
In-Reply-To: <20190408023746.16916-1-sjhuang@iluvatar.ai>
References: <20190408023746.16916-1-sjhuang@iluvatar.ai>
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Sender: linux-kernel-owner@vger.kernel.org
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The get_user_pages_fast() may mess up the page order in @pages array,
We will get the wrong DMA results in this case.

Add more commit to clarify it.

Signed-off-by: Huang Shijie <sjhuang@iluvatar.ai>
---
 lib/scatterlist.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 739dc9fe2c55..c170afb1a25e 100644
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -450,6 +450,9 @@ EXPORT_SYMBOL(__sg_alloc_table_from_pages);
  *    specified by the page array. The returned sg table is released by
  *    sg_free_table.
  *
+ * Note: Do not use get_user_pages_fast() to pin the pages for @pages array,
+ *       it may mess up the page order, and we will get the wrong DMA results.
+
  * Returns:
  *   0 on success, negative error on failure
  */
-- 
2.17.1