[PATCH] PSI: select KERNFS as needed

[Randy Dunlap <rdunlap@infradead.org>]

Users of KERNFS should select it to enforce its being built, so
do this to prevent a build error.

In file included from ../kernel/sched/build_utility.c:97:
../kernel/sched/psi.c: In function 'psi_trigger_poll':
../kernel/sched/psi.c:1479:17: error: implicit declaration of function 'kernfs_generic_poll' [-Werror=implicit-function-declaration]
 1479 |                 kernfs_generic_poll(t->of, wait);

Fixes: aff037078eca ("sched/psi: use kernfs polling functions for PSI trigger polling")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Link: lore.kernel.org/r/202307310732.r65EQFY0-lkp@intel.com
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
---
 init/Kconfig |    1 +
 1 file changed, 1 insertion(+)

diff -- a/init/Kconfig b/init/Kconfig
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -629,6 +629,7 @@ config TASK_IO_ACCOUNTING
 
 config PSI
 	bool "Pressure stall information tracking"
+	select KERNFS
 	help
 	  Collect metrics that indicate how overcommitted the CPU, memory,
 	  and IO capacity are in the system.