[PATCH 5.10 149/406] md/bitmap: dont set max_write_behind if there is no write mostly device

Greg Kroah-Hartman
2023-09-17T19:26:50Z

From: Guoqing Jiang <guoqing.jiang@linux.dev>

[ 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>
---
drivers/md/md-bitmap.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index f843ade442dec..eb8a2d5ba83f4 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 */
--
2.40.1