linux-kernel - [PATCH] mm: ratelimit end_swap_bio

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Message-Id: <20180106043407.25193-1-sergey.senozhatsky@gmail.com>
Date:   Sat,  6 Jan 2018 13:34:07 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Minchan Kim <minchan@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [PATCH] mm: ratelimit end_swap_bio_write() error

Use the ratelimited printk() version for swap-device write error
reporting. We can use ZRAM as a swap-device, and the tricky part
here is that zsmalloc() stores compressed objects in memory, thus
it has to allocates pages during swap-out. If the system is short
on memory, then we begin to flood printk() log buffer with the
same "Write-error on swap-device XXX" error messages and sometimes
simply lockup the system.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
---
 mm/page_io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index e93f1a4cacd7..422cd49bcba8 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -63,7 +63,7 @@ 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",
+		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);
-- 
2.15.1