mm: simplify nodemask printing

alloc_warn() and dump_header() have to explicitly handle NULL nodemask
which forces both paths to use pr_cont.  We can do better.  printk
already handles NULL pointers properly so all we need is to teach
nodemask_pr_args to handle NULL nodemask carefully.  This allows
simplification of both alloc_warn() and dump_header() and gets rid of
pr_cont altogether.

This patch has been motivated by patch from Joe Perches

  http://lkml.kernel.org/r/b31236dfe3fc924054fd7842bde678e71d193638.1509991345.git.joe@perches.com

[akpm@linux-foundation.org: fix tile warning, per Arnd]
Link: http://lkml.kernel.org/r/20171109100531.3cn2hcqnuj7mjaju@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Joe Perches <joe@perches.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 10 insertions, 18 deletions

diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index de1c50b93c61..15cab3967d6d 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -104,7 +104,9 @@ extern nodemask_t _unused_nodemask_arg_;
  *
  * Can be used to provide arguments for '%*pb[l]' when printing a nodemask.
  */
-#define nodemask_pr_args(maskp)         MAX_NUMNODES, (maskp)->bits
+#define nodemask_pr_args(maskp)                         \
+        ((maskp) != NULL) ? MAX_NUMNODES : 0,           \
+        ((maskp) != NULL) ? (maskp)->bits : NULL
 
 /*
  * The inline keyword gives the compiler room to decide to inline, or
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index a501a0a1f0f8..c86fbd1b590e 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -426,14 +426,10 @@ static void dump_tasks(struct mem_cgroup *memcg, const nodemask_t *nodemask)
 
 static void dump_header(struct oom_control *oc, struct task_struct *p)
 {
-        pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=",
-                current->comm, oc->gfp_mask, &oc->gfp_mask);
-        if (oc->nodemask)
-                pr_cont("%*pbl", nodemask_pr_args(oc->nodemask));
-        else
-                pr_cont("(null)");
-        pr_cont(",  order=%d, oom_score_adj=%hd\n",
-                oc->order, current->signal->oom_score_adj);
+        pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n",
+                current->comm, oc->gfp_mask, &oc->gfp_mask,
+                nodemask_pr_args(oc->nodemask), oc->order,
+                        current->signal->oom_score_adj);
         if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
                 pr_warn("COMPACTION is disabled!!!\n");
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8f2b9ad2e23f..7a199767dcee 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3279,20 +3279,14 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
         if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs))
                 return;
 
-        pr_warn("%s: ", current->comm);
-
         va_start(args, fmt);
         vaf.fmt = fmt;
         vaf.va = &args;
-        pr_cont("%pV", &vaf);
+        pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=%*pbl\n",
+                        current->comm, &vaf, gfp_mask, &gfp_mask,
+                        nodemask_pr_args(nodemask));
         va_end(args);
 
-        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();