>From 08a638e04351386ab03cd1223988ac7940d4d3aa Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Sat, 1 Aug 2015 22:46:12 +0900
Subject: [PATCH 2/2] mm: Fix potentically scheduling in GFP_ATOMIC
allocations.
Currently, if somebody does GFP_ATOMIC | __GFP_NOFAIL allocation,
wait_iff_congested() might be called via __alloc_pages_high_priority()
before reaching
if (!wait) {
WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL);
goto nopage;
}
because gfp_to_alloc_flags() includes ALLOC_NO_WATERMARKS if TIF_MEMDIE
was set.
We need to check for __GFP_WAIT flag at __alloc_pages_high_priority()
in order to make sure that we won't schedule.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 37a0390..f9f09fa 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2917,16 +2917,15 @@ __alloc_pages_high_priority(gfp_t gfp_mask, unsigned int order,
{
struct page *page;
- do {
+ for (;;) {
page = get_page_from_freelist(gfp_mask, order,
ALLOC_NO_WATERMARKS, ac);
- if (!page && gfp_mask & __GFP_NOFAIL)
- wait_iff_congested(ac->preferred_zone, BLK_RW_ASYNC,
- HZ/50);
- } while (!page && (gfp_mask & __GFP_NOFAIL));
-
- return page;
+ if (page || (gfp_mask & (__GFP_NOFAIL | __GFP_WAIT)) !=
+ (__GFP_NOFAIL | __GFP_WAIT))
+ return page;
+ wait_iff_congested(ac->preferred_zone, BLK_RW_ASYNC, HZ/50);
+ }
}
static void wake_all_kswapds(unsigned int order, const struct alloc_context *ac)
--
1.8.3.1
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