[PATCH 1/2] mm: replace custom bad page map ratelimiting logic

[Pedro Falcato]

The current logic (allow up to $BURST prints per minute) can be entirely
replaced by the generic version in lib/ratelimit.c, used around the kernel.

Do so. The only functional difference should be that the new logs will
read something like:

KERN_WARNING "print_bad_page_map: %d callbacks suppressed\n", ...

But that should be fine enough.

Signed-off-by: Pedro Falcato <pfalcato@xxxxxxx>
---
 mm/memory.c | 30 +++---------------------------
 1 file changed, 3 insertions(+), 27 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 4134ac607ee0..b4be57b590ce 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -492,32 +492,8 @@ static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
 			add_mm_counter(mm, i, rss[i]);
 }
 
-static bool is_bad_page_map_ratelimited(void)
-{
-	static unsigned long resume;
-	static unsigned long nr_shown;
-	static unsigned long nr_unshown;
-
-	/*
-	 * Allow a burst of 60 reports, then keep quiet for that minute;
-	 * or allow a steady drip of one report per second.
-	 */
-	if (nr_shown == 60) {
-		if (time_before(jiffies, resume)) {
-			nr_unshown++;
-			return true;
-		}
-		if (nr_unshown) {
-			pr_alert("BUG: Bad page map: %lu messages suppressed\n",
-				 nr_unshown);
-			nr_unshown = 0;
-		}
-		nr_shown = 0;
-	}
-	if (nr_shown++ == 0)
-		resume = jiffies + 60 * HZ;
-	return false;
-}
+/* Allow a burst of 60 bad page map reports per minute. */
+static DEFINE_RATELIMIT_STATE(bad_page_map_ratelimit, 60 * HZ, 60);
 
 static void ptval_bytes_to_hex_str(char *buf, size_t buf_size, const void *entry, size_t entry_size)
 {
@@ -633,7 +609,7 @@ static void print_bad_page_map(struct vm_area_struct *vma,
 	char entry_str[PTVAL_STR_MAX];
 	pgoff_t index, anon_index;
 
-	if (is_bad_page_map_ratelimited())
+	if (!__ratelimit(&bad_page_map_ratelimit))
 		return;
 
 	mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
-- 
2.55.0