"echo 1 > writeback_running" marks writeback_running even if no writeback
kthread created as "d_strtoul(writeback_running)" will simply set dc->
writeback_running without checking the existence of dc->writeback_thread.
Add check for setting writeback_running via sysfs:
* if no writeback kthread alive, reject setting to 1
* if writeback kthread alive, reject setting to 0
* consider none-0 values as true
Signed-off-by: Shenghui Wang <shhuiw@xxxxxxxxxxx>
---
drivers/md/bcache/sysfs.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 26f035a0c5b9..8e41f46c3f42 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -384,8 +384,30 @@ STORE(bch_cached_dev)
mutex_lock(&bch_register_lock);
size = __cached_dev_store(kobj, attr, buf, size);
- if (attr == &sysfs_writeback_running)
- bch_writeback_queue(dc);
+ if (attr == &sysfs_writeback_running) {
+ /* if set wrong value via sysfs, reset to previous value */
+ if (!IS_ERR_OR_NULL(dc->writeback_thread)) {
+ if (!dc->writeback_running)
+ pr_err("%s: cannot stop running writeback thread",
+ dc->backing_dev_name);
+ else
+ /* wake up if alive already. */
+ bch_writeback_queue(dc);
+
+ /* all none-0 values are considered as true */
+ dc->writeback_running = true;
+ } else {
+ /*
+ * reject setting it to 1 via sysfs if writeback
+ * kthread is not created yet.
+ */
+ if (dc->writeback_running) {
+ dc->writeback_running = false;
+ pr_err("%s: writeback thread not created yet",
+ dc->backing_dev_name);
+ }
+ }
+ }
if (attr == &sysfs_writeback_percent)
if (!test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags))
--
2.18.0
