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From:   Georgi Djakov <georgi.djakov@linaro.org>
To:     akpm@linux-foundation.org
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Georgi Djakov <georgi.djakov@linaro.org>
Subject: [PATCH] mm/page_io: Use pr_alert_ratelimited for swap read/write errors
Date:   Mon,  1 Feb 2021 16:20:55 +0200
Message-Id: <20210201142055.29068-1-georgi.djakov@linaro.org>
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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.

Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
---
 mm/page_io.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index 92f7941c6d01..485fa5cca4a2 100644
--- a/mm/page_io.c
+++ b/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;
 	}