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>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a179607de26f0c03e062361954d732bd9cea5262..c21b336681334f33f13cc6a203f30e0a7ca389bf 100644 (file)
--- 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 *