mm, page_alloc: warn_alloc nodemask is NULL when cpusets are disabled

The patch "mm, page_alloc: warn_alloc print nodemask" implicitly sets
the allocation nodemask to cpuset_current_mems_allowed when there is no
effective mempolicy.  cpuset_current_mems_allowed is only effective when
cpusets are enabled, which is also printed by warn_alloc(), so setting
the nodemask to cpuset_current_mems_allowed is redundant and prevents
debugging issues where ac->nodemask is not set properly in the page
allocator.

This provides better debugging output since
cpuset_print_current_mems_allowed() is already provided.

Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1701181347320.142399@chino.kir.corp.google.com
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 3 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a179607de26f..c21b33668133 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3034,7 +3034,6 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
         va_list args;
         static DEFINE_RATELIMIT_STATE(nopage_rs, DEFAULT_RATELIMIT_INTERVAL,
                                       DEFAULT_RATELIMIT_BURST);
-        nodemask_t *nm = (nodemask) ? nodemask : &cpuset_current_mems_allowed;
 
         if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) ||
             debug_guardpage_minorder() > 0)
@@ -3048,11 +3047,16 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
         pr_cont("%pV", &vaf);
         va_end(args);
 
-        pr_cont(", mode:%#x(%pGg), nodemask=%*pbl\n", gfp_mask, &gfp_mask, nodemask_pr_args(nm));
+        pr_cont(", mode:%#x(%pGg), nodemask=", gfp_mask, &gfp_mask);
+        if (nodemask)
+                pr_cont("%*pbl\n", nodemask_pr_args(nodemask));
+        else
+                pr_cont("(null)\n");
+
         cpuset_print_current_mems_allowed();
 
         dump_stack();
-        warn_alloc_show_mem(gfp_mask, nm);
+        warn_alloc_show_mem(gfp_mask, nodemask);
 }
 
 static inline struct page *