"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
available, reject setting to 1.
v2 -> v3:
* Make message on wrong assignment more clear.
* Print name of bcache device instead of name of backing device.
Signed-off-by: Shenghui Wang <shhuiw@xxxxxxxxxxx>
---
drivers/md/bcache/sysfs.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 26f035a0c5b9..3932fd548d4b 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -384,8 +384,25 @@ 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) {
+ /* dc->writeback_running changed in __cached_dev_store() */
+ if (IS_ERR_OR_NULL(dc->writeback_thread)) {
+ /*
+ * 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: failed to run non-existent writeback thread",
+ dc->disk.disk->disk_name);
+ }
+ } else
+ /*
+ * writeback kthread will check if dc->writeback_running
+ * is true or false.
+ */
+ bch_writeback_queue(dc);
+ }
if (attr == &sysfs_writeback_percent)
if (!test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags))
--
2.18.0
