>From 7e4775600798d24680ff449412f2d0479711948c Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 2 Jun 2015 21:14:28 +0900
Subject: [PATCH] mm: Fix theoretical sleeping in atomic.
We could theoretically be too late to warn on
(gfp_mask & (__GFP_NOFAIL | __GFP_WAIT)) == __GFP_NOFAIL
if get_page_from_freelist(ALLOC_NO_WATERMARKS) failed at
__alloc_pages_high_priority(), for wait_iff_congested() in
__alloc_pages_high_priority() might have already slept for
kmalloc(GFP_ATOMIC | __GFP_NOFAIL) allocation request because
ALLOC_NO_WATERMARKS can be automatically supplied due to
e.g. TIF_MEMDIE.
Make sure that __alloc_pages_high_priority() will not loop
unless both __GFP_NOFAIL and __GFP_WAIT are given.
Maybe
if (!wait)
WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL);
part should be moved to immediately after
if (order >= MAX_ORDER) {
WARN_ON_ONCE(!(gfp_mask & __GFP_NOWARN));
return NULL;
}
?
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 73aa335..187a0b5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2880,16 +2880,15 @@ __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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