[PATCH] mm/hugetlb: hugetlb_no_page: Rate-limit warning message

[Geoffrey Thomas <geofft@ldpreload.com>]

The warning message "killed due to inadequate hugepage pool" simply 
indicates that SIGBUS was sent, not that the process was forcibly killed. 
If the process has a signal handler installed does not fix the problem, 
this message can rapidly spam the kernel log.

Signed-off-by: Geoffrey Thomas <geofft@ldpreload.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
On my amd64 dev machine that does not have hugepages configured, I can 
reproduce the repeated warnings easily by setting vm.nr_hugepages=2 (i.e., 
4 megabytes of huge pages) and running something that sets a signal 
handler and forks, like

#include <sys/mman.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>

sig_atomic_t counter = 10;
void handler(int signal) {
 	if (counter-- == 0)
 		exit(0);
}

int main(void) {
 	int status;
 	char *addr = mmap(NULL, 4 * 1048576, PROT_READ | PROT_WRITE,
 			  MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0);
 	if (addr == MAP_FAILED) {perror("mmap"); return 1;}
 	*addr = 'x';
 	switch (fork()) {
 		case -1:
 			perror("fork"); return 1;
 		case 0:
 			signal(SIGBUS, handler);
 			*addr = 'x';
 			break;
 		default:
 			*addr = 'x';
 			wait(&status);
 			if (WIFSIGNALED(status)) {
 				psignal(WTERMSIG(status), "child");
 			}
 			break;
 	}
}

  mm/hugetlb.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 01f2b48..0e27a9d 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3502,7 +3502,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
  	 * COW. Warn that such a situation has occurred as it may not be obvious
  	 */
  	if (is_vma_resv_set(vma, HPAGE_RESV_UNMAPPED)) {
-		pr_warning("PID %d killed due to inadequate hugepage pool\n",
+		pr_warn_ratelimited("PID %d killed due to inadequate hugepage pool\n",
  			   current->pid);
  		return ret;
  	}
-- 
2.1.4

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