The patch titled
Subject: mm: drop VM_BUG_ON from __get_free_pages
has been added to the -mm tree. Its filename is
mm-drop-vm_bug_on-from-__get_free_pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-drop-vm_bug_on-from-__get_free_pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-drop-vm_bug_on-from-__get_free_pages.patch
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------------------------------------------------------
From: Michal Hocko <mhocko@xxxxxxxx>
Subject: 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.
Link: http://lkml.kernel.org/r/20180622162841.25114-1-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Jiankang Chen <chenjiankang1@xxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Yisheng Xie <xieyisheng1@xxxxxxxxxx>
Cc: Hanjun Guo <guohanjun@xxxxxxxxxx>
Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 10 +++-------
1 file changed, 3 insertions(+), 7 deletions(-)
diff -puN mm/page_alloc.c~mm-drop-vm_bug_on-from-__get_free_pages mm/page_alloc.c
--- a/mm/page_alloc.c~mm-drop-vm_bug_on-from-__get_free_pages
+++ a/mm/page_alloc.c
@@ -4403,18 +4403,14 @@ out:
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);
if (!page)
return 0;
_
Patches currently in -mm which might be from mhocko@xxxxxxxx are
mm-drop-vm_bug_on-from-__get_free_pages.patch
mm-oom-docs-describe-the-cgroup-aware-oom-killer-fix-2.patch
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