[PATCH 5.10 150/406] md/md-bitmap: hold reconfig_mutex in backlog_store()

Greg Kroah-Hartman
2023-09-17T19:26:51Z

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit 44abfa6a95df425c0660d56043020b67e6d93ab8 ]

Several reasons why 'reconfig_mutex' should be held:

1) rdev_for_each() is not safe to be called without the lock, because
rdev can be removed concurrently.
2) mddev_destroy_serial_pool() and mddev_create_serial_pool() should not
be called concurrently.
3) mddev_suspend() from mddev_destroy/create_serial_pool() should be
protected by the lock.

Fixes: 10c92fca636e ("md-bitmap: create and destroy wb_info_pool with the change of backlog")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20230706083727.608914-3-yukuai1@huaweicloud.com
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/md/md-bitmap.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index eb8a2d5ba83f4..d18ca119929e1 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -2484,6 +2484,10 @@ backlog_store(struct mddev *mddev, const char *buf, size_t len)
if (backlog > COUNTER_MAX)
return -EINVAL;

+ rv = mddev_lock(mddev);
+ if (rv)
+ return rv;
+
/*
* Without write mostly device, it doesn't make sense to set
* backlog for max_write_behind.
@@ -2497,6 +2501,7 @@ backlog_store(struct mddev *mddev, const char *buf, size_t len)
if (!has_write_mostly) {
pr_warn_ratelimited("%s: can't set backlog, no write mostly device available\n",
mdname(mddev));
+ mddev_unlock(mddev);
return -EINVAL;
}

@@ -2514,6 +2519,8 @@ backlog_store(struct mddev *mddev, const char *buf, size_t len)
}
if (old_mwb != backlog)
md_bitmap_update_sb(mddev->bitmap);
+
+ mddev_unlock(mddev);
return len;
}

--
2.40.1