[PATCH v4 2/2] f2fs: protect critical_task_priority updates with s_umount

[Wenjie Qi]

The sysfs store path already takes s_umount for GC thread control
entries, and ckpt_thread_ioprio is covered as well.

critical_task_priority also updates checkpoint or GC kthread scheduling
state, but it is not covered by that serialization. It can race with
remount or teardown paths that are stopping those threads.

Protect critical_task_priority sysfs writes with s_umount too.

Fixes: 52190933c37a ("f2fs: sysfs: introduce critical_task_priority")
Cc: stable@xxxxxxxxxx
Signed-off-by: Wenjie Qi <qiwenjie@xxxxxxxxxx>
---
v4:
- add Fixes tag
- add Cc: stable@xxxxxxxxxx
---
 fs/f2fs/sysfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 0729b3670415..aa1621419932 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -1007,7 +1007,8 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a,
 	ssize_t ret;
 	bool gc_entry = (!strcmp(a->attr.name, "gc_urgent") ||
 					a->struct_type == GC_THREAD);
-	bool thread_entry = !strcmp(a->attr.name, "ckpt_thread_ioprio");
+	bool thread_entry = !strcmp(a->attr.name, "ckpt_thread_ioprio") ||
+			!strcmp(a->attr.name, "critical_task_priority");
 
 	if (gc_entry || thread_entry) {
 		if (!down_read_trylock(&sbi->sb->s_umount))
-- 
2.43.0