mm/page_io: use pr_alert_ratelimited for swap read/write errors

If there are errors during swap read or write, they can easily fill the
log buffer and remove any previous messages that might be useful for
debugging, especially on systems that rely for logging only on the kernel
ring-buffer.

For example, on a systems using zram as swap, we are more likely to see
any page allocation errors preceding the swap write errors if the alerts
are ratelimited.

Link: https://lkml.kernel.org/r/20210201142055.29068-1-georgi.djakov@linaro.org
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_io.c

@@ -41,9 +41,9 @@ void end_swap_bio_write(struct bio *bio)
 		 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
 		 */
 		set_page_dirty(page);
-		pr_alert("Write-error on swap-device (%u:%u:%llu)\n",
-			 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
-			 (unsigned long long)bio->bi_iter.bi_sector);
+		pr_alert_ratelimited("Write-error on swap-device (%u:%u:%llu)\n",
+				     MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
+				     (unsigned long long)bio->bi_iter.bi_sector);
 		ClearPageReclaim(page);
 	}
 	end_page_writeback(page);
@@ -106,9 +106,9 @@ static void end_swap_bio_read(struct bio *bio)
 	if (bio->bi_status) {
 		SetPageError(page);
 		ClearPageUptodate(page);
-		pr_alert("Read-error on swap-device (%u:%u:%llu)\n",
-			 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
-			 (unsigned long long)bio->bi_iter.bi_sector);
+		pr_alert_ratelimited("Read-error on swap-device (%u:%u:%llu)\n",
+				     MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
+				     (unsigned long long)bio->bi_iter.bi_sector);
 		goto out;
 	}