[Adding Andrew into CC]
Hi Dan,
On Wed 27-03-13 09:01:42, Dan Carpenter wrote:
> Hello Mel Gorman,
>
> The patch 290d1a3ce0ec: "mm: page_alloc: avoid marking zones full
> prematurely after zone_reclaim()" from Mar 23, 2013, leads to the
> following warning:
> "mm/page_alloc.c:1957 get_page_from_freelist()
> warn: bitwise AND condition is false here"
Dohh, I have totally missed this during review and I managed to burn
myself on the similar issue in the past (gfp & GFP_NOWAIT).
The follow up fix is bellow
> mm/page_alloc.c
> 1948 /*
> 1949 * Failed to reclaim enough to meet watermark.
> 1950 * Only mark the zone full if checking the min
> 1951 * watermark or if we failed to reclaim just
> 1952 * 1<<order pages or else the page allocator
> 1953 * fastpath will prematurely mark zones full
> 1954 * when the watermark is between the low and
> 1955 * min watermarks.
> 1956 */
> 1957 if ((alloc_flags & ALLOC_WMARK_MIN) ||
> ^^^^^^^^^^^^^^^
> This is zero.
>
> 1958 ret == ZONE_RECLAIM_SOME)
> 1959 goto this_zone_full;
>
> [snip]
>
> 2333 static inline int
> 2334 gfp_to_alloc_flags(gfp_t gfp_mask)
> 2335 {
> 2336 int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
> ^^^^^^^^^^^^^^^
> 2337 const gfp_t wait = gfp_mask & __GFP_WAIT;
---
>From b60e75c65b855a0df827a28a509e6761b4cf45dd Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@xxxxxxx>
Date: Wed, 27 Mar 2013 17:53:09 +0100
Subject: [PATCH] mm:
mm-page_alloc-avoid-marking-zones-full-prematurely-after-zone_reclaim-fix
Dan Carpenter has reported that (alloc_flags & ALLOC_WMARK_MIN) test
doesn't make much sense as the flag is 0 and it is in fact intended for
wmark indexing rather than being used as a flag.
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
---
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index aa4b5c2..071e66a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1953,7 +1953,7 @@ zonelist_scan:
* when the watermark is between the low and
* min watermarks.
*/
- if ((alloc_flags & ALLOC_WMARK_MIN) ||
+ if (((alloc_flags & ALLOC_WMARK_MASK) == ALLOC_WMARK_MIN) ||
ret == ZONE_RECLAIM_SOME)
goto this_zone_full;
--
1.7.10.4
--
Michal Hocko
SUSE Labs
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