From 9ea9a68064035dee70f465f605a3e63990e33bd9 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@suse.com>
Date: Fri, 17 Aug 2018 15:46:01 -0700
Subject: [PATCH] mm: drop VM_BUG_ON from __get_free_pages
There is no real reason to blow up just because the caller doesn't know
that __get_free_pages cannot return highmem pages. Simply fix that up
silently. Even if we have some confused users such a fixup will not be
harmful.
[akpm@linux-foundation.org: mask off __GFP_HIGHMEM]
Link: http://lkml.kernel.org/r/20180622162841.25114-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiankang Chen <chenjiankang1@huawei.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yisheng Xie <xieyisheng1@huawei.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/page_alloc.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0303a3b246109..e1517bb143dc6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4404,19 +4404,15 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, int preferred_nid,
EXPORT_SYMBOL(__alloc_pages_nodemask);
/*
- * Common helper functions.
+ * Common helper functions. Never use with __GFP_HIGHMEM because the returned
+ * address cannot represent highmem pages. Use alloc_pages and then kmap if
+ * you need to access high mem.
*/
unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
{
struct page *page;
- /*
- * __get_free_pages() returns a virtual address, which cannot represent
- * a highmem page
- */
- VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
-
- page = alloc_pages(gfp_mask, order);
+ page = alloc_pages(gfp_mask & ~__GFP_HIGHMEM, order);
if (!page)
return 0;
return (unsigned long) page_address(page);
--
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