md/r5cache: call mddev_lock/unlock() in r5c_journal_mode_show
In r5c_journal_mode_show(), it is necessary to call mddev_lock()
before accessing conf and conf->log. Otherwise, the conf->log
may change (and become NULL).
Signed-off-by: Song Liu <songliubraving@fb.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 2dcbafa..e357ed3 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -2529,11 +2529,18 @@
static ssize_t r5c_journal_mode_show(struct mddev *mddev, char *page)
{
- struct r5conf *conf = mddev->private;
+ struct r5conf *conf;
int ret;
- if (!conf->log)
+ ret = mddev_lock(mddev);
+ if (ret)
+ return ret;
+
+ conf = mddev->private;
+ if (!conf || !conf->log) {
+ mddev_unlock(mddev);
return 0;
+ }
switch (conf->log->r5c_journal_mode) {
case R5C_JOURNAL_MODE_WRITE_THROUGH:
@@ -2551,6 +2558,7 @@
default:
ret = 0;
}
+ mddev_unlock(mddev);
return ret;
}