[PATCH] fs/ceph/mds_client: use cap_wait_list only if debugfs is enabled

[Max Kellermann]

Only debugfs uses this list.  By omitting it, we save some memory and
reduce lock contention on `caps_list_lock`.

Signed-off-by: Max Kellermann <max.kellermann@xxxxxxxxx>
---
 fs/ceph/caps.c       | 6 ++++++
 fs/ceph/mds_client.c | 2 ++
 fs/ceph/mds_client.h | 6 ++++++
 3 files changed, 14 insertions(+)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index c4941ba245ac..772879aa26ee 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -3067,10 +3067,13 @@ int __ceph_get_caps(struct inode *inode, struct ceph_file_info *fi, int need,
 				       flags, &_got);
 		WARN_ON_ONCE(ret == -EAGAIN);
 		if (!ret) {
+#ifdef CONFIG_DEBUG_FS
 			struct ceph_mds_client *mdsc = fsc->mdsc;
 			struct cap_wait cw;
+#endif
 			DEFINE_WAIT_FUNC(wait, woken_wake_function);
 
+#ifdef CONFIG_DEBUG_FS
 			cw.ino = ceph_ino(inode);
 			cw.tgid = current->tgid;
 			cw.need = need;
@@ -3079,6 +3082,7 @@ int __ceph_get_caps(struct inode *inode, struct ceph_file_info *fi, int need,
 			spin_lock(&mdsc->caps_list_lock);
 			list_add(&cw.list, &mdsc->cap_wait_list);
 			spin_unlock(&mdsc->caps_list_lock);
+#endif // CONFIG_DEBUG_FS
 
 			/* make sure used fmode not timeout */
 			ceph_get_fmode(ci, flags, FMODE_WAIT_BIAS);
@@ -3097,9 +3101,11 @@ int __ceph_get_caps(struct inode *inode, struct ceph_file_info *fi, int need,
 			remove_wait_queue(&ci->i_cap_wq, &wait);
 			ceph_put_fmode(ci, flags, FMODE_WAIT_BIAS);
 
+#ifdef CONFIG_DEBUG_FS
 			spin_lock(&mdsc->caps_list_lock);
 			list_del(&cw.list);
 			spin_unlock(&mdsc->caps_list_lock);
+#endif
 
 			if (ret == -EAGAIN)
 				continue;
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index c2157f6e0c69..62238f3e6e19 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -5505,7 +5505,9 @@ int ceph_mdsc_init(struct ceph_fs_client *fsc)
 	INIT_DELAYED_WORK(&mdsc->delayed_work, delayed_work);
 	mdsc->last_renew_caps = jiffies;
 	INIT_LIST_HEAD(&mdsc->cap_delay_list);
+#ifdef CONFIG_DEBUG_FS
 	INIT_LIST_HEAD(&mdsc->cap_wait_list);
+#endif
 	spin_lock_init(&mdsc->cap_delay_lock);
 	INIT_LIST_HEAD(&mdsc->cap_unlink_delay_list);
 	INIT_LIST_HEAD(&mdsc->snap_flush_list);
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index cfa18cf915a0..13dd83f783ec 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -416,6 +416,8 @@ struct ceph_quotarealm_inode {
 	struct inode *inode;
 };
 
+#ifdef CONFIG_DEBUG_FS
+
 struct cap_wait {
 	struct list_head	list;
 	u64			ino;
@@ -424,6 +426,8 @@ struct cap_wait {
 	int			want;
 };
 
+#endif // CONFIG_DEBUG_FS
+
 enum {
 	CEPH_MDSC_STOPPING_BEGIN = 1,
 	CEPH_MDSC_STOPPING_FLUSHING = 2,
@@ -512,7 +516,9 @@ struct ceph_mds_client {
 	spinlock_t	caps_list_lock;
 	struct		list_head caps_list; /* unused (reserved or
 						unreserved) */
+#ifdef CONFIG_DEBUG_FS
 	struct		list_head cap_wait_list;
+#endif
 	int		caps_total_count;    /* total caps allocated */
 	int		caps_use_count;      /* in use */
 	int		caps_use_max;	     /* max used caps */
-- 
2.39.2