On 12/16/2014 12:43 AM, Andrew Morton wrote:
On Tue, 16 Dec 2014 08:32:36 +0900 Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx> wrote:
(2014/12/16 8:03), akpm@xxxxxxxxxxxxxxxxxxxx wrote:
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: mm/page_alloc.c:__alloc_pages_nodemask(): don't alter arg gfp_mask
__alloc_pages_nodemask() strips __GFP_IO when retrying the page
allocation. But it does this by altering the function-wide variable
gfp_mask. This will cause subsequent allocation attempts to inadvertently
use the modified gfp_mask.
Cc: Ming Lei <ming.lei@xxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff -puN mm/page_alloc.c~mm-page_allocc-__alloc_pages_nodemask-dont-alter-arg-gfp_mask mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_allocc-__alloc_pages_nodemask-dont-alter-arg-gfp_mask
+++ a/mm/page_alloc.c
@@ -2918,8 +2918,9 @@ retry_cpuset:
* can deadlock because I/O on the device might not
* complete.
*/
- gfp_mask = memalloc_noio_flags(gfp_mask);
- page = __alloc_pages_slowpath(gfp_mask, order,
+ gfp_t mask = memalloc_noio_flags(gfp_mask);
+
+ page = __alloc_pages_slowpath(mask, order,
zonelist, high_zoneidx, nodemask,
preferred_zone, classzone_idx, migratetype);
}
After allocating page, trace_mm_page_alloc(page, order, gfp_mask, migratetype)
is called. But mask is not passed to it. So trace_mm_page_alloc traces wrong
gfp_mask.
Well it was already wrong because the first allocation attempt uses
gfp_mask|__GFP_HARDWAL, but we only trace gfp_mask.
If we wanted to be 100% correct with the tracepoint, then there's also
__alloc_pages_may_oom(), which also appends __GFP_HARDWALL on the fly
page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask,
But fixing that would be ugly :/ I guess it's not worth the trouble.
This?
--- a/mm/page_alloc.c~mm-page_allocc-__alloc_pages_nodemask-dont-alter-arg-gfp_mask-fix
+++ a/mm/page_alloc.c
@@ -2877,6 +2877,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, u
unsigned int cpuset_mems_cookie;
int alloc_flags = ALLOC_WMARK_LOW|ALLOC_CPUSET|ALLOC_FAIR;
int classzone_idx;
+ gfp_t mask;
gfp_mask &= gfp_allowed_mask;
@@ -2910,23 +2911,24 @@ retry_cpuset:
classzone_idx = zonelist_zone_idx(preferred_zoneref);
/* First allocation attempt */
- page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask, order,
- zonelist, high_zoneidx, alloc_flags,
- preferred_zone, classzone_idx, migratetype);
+ mask = gfp_mask|__GFP_HARDWALL;
+ page = get_page_from_freelist(mask, nodemask, order, zonelist,
+ high_zoneidx, alloc_flags, preferred_zone,
+ classzone_idx, migratetype);
if (unlikely(!page)) {
/*
* Runtime PM, block IO and its error handling path
* can deadlock because I/O on the device might not
* complete.
*/
- gfp_t mask = memalloc_noio_flags(gfp_mask);
+ mask = memalloc_noio_flags(gfp_mask);
page = __alloc_pages_slowpath(mask, order,
zonelist, high_zoneidx, nodemask,
preferred_zone, classzone_idx, migratetype);
}
- trace_mm_page_alloc(page, order, gfp_mask, migratetype);
+ trace_mm_page_alloc(page, order, mask, migratetype);
out:
/*
_
--
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