From ca7dc242e358e46d963b32f9d9dd829785a9e957 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Wed, 13 Jul 2022 07:09:04 -0400
Subject: [PATCH] dm writecache: set a default MAX_WRITEBACK_JOBS
Git-commit: ca7dc242e358e46d963b32f9d9dd829785a9e957
Patch-mainline: v6.0-rc1
References: jsc#PED-2765

dm-writecache has the capability to limit the number of writeback jobs
in progress. However, this feature was off by default. As such there
were some out-of-memory crashes observed when lowering the low
watermark while the cache is full.

This commit enables writeback limit by default. It is set to 256MiB or
1/16 of total system memory, whichever is smaller.

Cc: stable@vger.kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/dm-writecache.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index d74c5a7a0ab4..d572135cd43f 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -22,7 +22,7 @@
 
 #define HIGH_WATERMARK			50
 #define LOW_WATERMARK			45
-#define MAX_WRITEBACK_JOBS		0
+#define MAX_WRITEBACK_JOBS		min(0x10000000 / PAGE_SIZE, totalram_pages() / 16)
 #define ENDIO_LATENCY			16
 #define WRITEBACK_LATENCY		64
 #define AUTOCOMMIT_BLOCKS_SSD		65536
-- 
2.35.3