fs: don't compile in drop_caches.c when CONFIG_SYSCTL=n

drop_caches.c provides code only invokable via sysctl, so don't compile it
in when CONFIG_SYSCTL=n.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 43b70d5f8201..98a44376e4f3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1731,8 +1731,12 @@ int in_gate_area_no_mm(unsigned long addr);
 #define in_gate_area(mm, addr) ({(void)mm; in_gate_area_no_mm(addr);})
 #endif  /* __HAVE_ARCH_GATE_AREA */
 
+#ifdef CONFIG_SYSCTL
+extern int sysctl_drop_caches;
 int drop_caches_sysctl_handler(struct ctl_table *, int,
                                         void __user *, size_t *, loff_t *);
+#endif
+
 unsigned long shrink_slab(struct shrink_control *shrink,
                           unsigned long nr_pages_scanned,
                           unsigned long lru_pages);