fscache: Move fscache_cookies_seq_ops specific code under CONFIG_PROC_FS

fscache_cookies_seq_ops is only used in proc.c that is compiled under
enabled CONFIG_PROC_FS, so move related code under this config. The
same case exsits in internal.h.

Also, make fscache_lru_cookie_timeout static due to no user outside
of cookie.c.
Signed-off-by: Yue Hu <huyue2@coolpad.com>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-cachefs@redhat.com
Link: https://listman.redhat.com/archives/linux-cachefs/2022-April/006649.html # v1

fs/fscache/cookie.c

@@ -30,7 +30,7 @@ static DEFINE_SPINLOCK(fscache_cookie_lru_lock);
 DEFINE_TIMER(fscache_cookie_lru_timer, fscache_cookie_lru_timed_out);
 static DECLARE_WORK(fscache_cookie_lru_work, fscache_cookie_lru_worker);
 static const char fscache_cookie_states[FSCACHE_COOKIE_STATE__NR] = "-LCAIFUWRD";
-unsigned int fscache_lru_cookie_timeout = 10 * HZ;
+static unsigned int fscache_lru_cookie_timeout = 10 * HZ;
 
 void fscache_print_cookie(struct fscache_cookie *cookie, char prefix)
 {
@@ -1069,6 +1069,7 @@ void __fscache_invalidate(struct fscache_cookie *cookie,
 }
 EXPORT_SYMBOL(__fscache_invalidate);
 
+#ifdef CONFIG_PROC_FS
 /*
  * Generate a list of extant cookies in /proc/fs/fscache/cookies
  */
@@ -1145,3 +1146,4 @@ const struct seq_operations fscache_cookies_seq_ops = {
 	.stop   = fscache_cookies_seq_stop,
 	.show   = fscache_cookies_seq_show,
 };
+#endif

fs/fscache/internal.h

@@ -56,7 +56,9 @@ static inline bool fscache_set_cache_state_maybe(struct fscache_cache *cache,
  * cookie.c
  */
 extern struct kmem_cache *fscache_cookie_jar;
+#ifdef CONFIG_PROC_FS
 extern const struct seq_operations fscache_cookies_seq_ops;
+#endif
 extern struct timer_list fscache_cookie_lru_timer;
 
 extern void fscache_print_cookie(struct fscache_cookie *cookie, char prefix);
@@ -137,7 +139,9 @@ int fscache_stats_show(struct seq_file *m, void *v);
 /*
  * volume.c
  */
+#ifdef CONFIG_PROC_FS
 extern const struct seq_operations fscache_volumes_seq_ops;
+#endif
 
 struct fscache_volume *fscache_get_volume(struct fscache_volume *volume,
 					  enum fscache_volume_trace where);