From: Guoqing Jiang <guoqing.jiang@linux.dev>
Date: Sun, 17 Oct 2021 13:50:17 +0000 (+0800)
Subject: md/bitmap: don't set max_write_behind if there is no write mostly device
X-Git-Tag: v5.15.132~347
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=382638364711b5630d9e30982b36308e78de3231;p=thirdparty%2Fkernel%2Fstable.git

md/bitmap: don't set max_write_behind if there is no write mostly device

[ Upstream commit 8c13ab115b577bd09097b9d77916732e97e31b7b ]

We shouldn't set it since write behind IO should only happen to write
mostly device.

Signed-off-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Signed-off-by: Song Liu <songliubraving@fb.com>
Stable-dep-of: 44abfa6a95df ("md/md-bitmap: hold 'reconfig_mutex' in backlog_store()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index adada558a1b09..daedd9fcc4e5e 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -2476,11 +2476,30 @@ backlog_store(struct mddev *mddev, const char *buf, size_t len)
 {
 	unsigned long backlog;
 	unsigned long old_mwb = mddev->bitmap_info.max_write_behind;
+	struct md_rdev *rdev;
+	bool has_write_mostly = false;
 	int rv = kstrtoul(buf, 10, &backlog);
 	if (rv)
 		return rv;
 	if (backlog > COUNTER_MAX)
 		return -EINVAL;
+
+	/*
+	 * Without write mostly device, it doesn't make sense to set
+	 * backlog for max_write_behind.
+	 */
+	rdev_for_each(rdev, mddev) {
+		if (test_bit(WriteMostly, &rdev->flags)) {
+			has_write_mostly = true;
+			break;
+		}
+	}
+	if (!has_write_mostly) {
+		pr_warn_ratelimited("%s: can't set backlog, no write mostly device available\n",
+				    mdname(mddev));
+		return -EINVAL;
+	}
+
 	mddev->bitmap_info.max_write_behind = backlog;
 	if (!backlog && mddev->serial_info_pool) {
 		/* serial_info_pool is not needed if backlog is zero */