[PATCH v1] cifs: simplify SWN code with dummy funcs instead of ifdefs

["Aurélien Aptel" <aaptel@suse.com>]

From: Aurelien Aptel <aaptel@suse.com>

This commit doesn't change the logic of SWN.

Add dummy implementation of SWN functions when SWN is disabled instead
of using ifdef sections.

The dummy functions get optimized out, this leads to clearer code and
compile time type-checking regardless of config options with no
runtime penalty.

Leave the simple ifdefs section as-is.

A single bitfield (bool foo:1) on its own will use up one int. Move
tcon->use_witness out of ifdefs with the other tcon bitfields.

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
---
 fs/cifs/cifs_debug.c |  8 +-------
 fs/cifs/cifs_swn.h   | 27 +++++++++++++++++++++++++++
 fs/cifs/cifsfs.c     |  2 --
 fs/cifs/cifsglob.h   |  4 +---
 fs/cifs/connect.c    | 26 ++++----------------------
 5 files changed, 33 insertions(+), 34 deletions(-)

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index 0f3e64667a35..e19ddfb2b741 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -24,9 +24,7 @@
 #ifdef CONFIG_CIFS_SMB_DIRECT
 #include "smbdirect.h"
 #endif
-#ifdef CONFIG_CIFS_SWN_UPCALL
 #include "cifs_swn.h"
-#endif
 
 void
 cifs_dump_mem(char *label, void *data, int length)
@@ -119,10 +117,8 @@ static void cifs_debug_tcon(struct seq_file *m, struct cifs_tcon *tcon)
 		seq_printf(m, " POSIX Extensions");
 	if (tcon->ses->server->ops->dump_share_caps)
 		tcon->ses->server->ops->dump_share_caps(m, tcon);
-#ifdef CONFIG_CIFS_SWN_UPCALL
 	if (tcon->use_witness)
 		seq_puts(m, " Witness");
-#endif
 
 	if (tcon->need_reconnect)
 		seq_puts(m, "\tDISCONNECTED ");
@@ -491,10 +487,8 @@ static int cifs_debug_data_proc_show(struct seq_file *m, void *v)
 
 	spin_unlock(&cifs_tcp_ses_lock);
 	seq_putc(m, '\n');
-
-#ifdef CONFIG_CIFS_SWN_UPCALL
 	cifs_swn_dump(m);
-#endif
+
 	/* BB add code to dump additional info such as TCP session info now */
 	return 0;
 }
diff --git a/fs/cifs/cifs_swn.h b/fs/cifs/cifs_swn.h
index 236ecd4959d5..8a9d2a5c9077 100644
--- a/fs/cifs/cifs_swn.h
+++ b/fs/cifs/cifs_swn.h
@@ -7,11 +7,13 @@
 
 #ifndef _CIFS_SWN_H
 #define _CIFS_SWN_H
+#include "cifsglob.h"
 
 struct cifs_tcon;
 struct sk_buff;
 struct genl_info;
 
+#ifdef CONFIG_CIFS_SWN_UPCALL
 extern int cifs_swn_register(struct cifs_tcon *tcon);
 
 extern int cifs_swn_unregister(struct cifs_tcon *tcon);
@@ -22,4 +24,29 @@ extern void cifs_swn_dump(struct seq_file *m);
 
 extern void cifs_swn_check(void);
 
+static inline bool cifs_swn_set_server_dstaddr(struct TCP_Server_Info *server)
+{
+	if (server->use_swn_dstaddr) {
+		server->dstaddr = server->swn_dstaddr;
+		return true;
+	}
+	return false;
+}
+
+static inline void cifs_swn_reset_server_dstaddr(struct TCP_Server_Info *server)
+{
+	server->use_swn_dstaddr = false;
+}
+
+#else
+
+static inline int cifs_swn_register(struct cifs_tcon *tcon) { return 0; }
+static inline int cifs_swn_unregister(struct cifs_tcon *tcon) { return 0; }
+static inline int cifs_swn_notify(struct sk_buff *s, struct genl_info *i) { return 0; }
+static inline void cifs_swn_dump(struct seq_file *m) {}
+static inline void cifs_swn_check(void) {}
+static inline bool cifs_swn_set_server_dstaddr(struct TCP_Server_Info *server) { return false; }
+static inline void cifs_swn_reset_server_dstaddr(struct TCP_Server_Info *server) {}
+
+#endif /* CONFIG_CIFS_SWN_UPCALL */
 #endif /* _CIFS_SWN_H */
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 099ad9f3660b..58b9de3bd106 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -655,10 +655,8 @@ cifs_show_options(struct seq_file *s, struct dentry *root)
 		seq_printf(s, ",multichannel,max_channels=%zu",
 			   tcon->ses->chan_max);
 
-#ifdef CONFIG_CIFS_SWN_UPCALL
 	if (tcon->use_witness)
 		seq_puts(s, ",witness");
-#endif
 
 	return 0;
 }
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 31fc8695abd6..26df87a3bcbe 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -1070,6 +1070,7 @@ struct cifs_tcon {
 	bool use_resilient:1; /* use resilient instead of durable handles */
 	bool use_persistent:1; /* use persistent instead of durable handles */
 	bool no_lease:1;    /* Do not request leases on files or directories */
+	bool use_witness:1; /* use witness protocol */
 	__le32 capabilities;
 	__u32 share_flags;
 	__u32 maximal_access;
@@ -1094,9 +1095,6 @@ struct cifs_tcon {
 	int remap:2;
 	struct list_head ulist; /* cache update list */
 #endif
-#ifdef CONFIG_CIFS_SWN_UPCALL
-	bool use_witness:1; /* use witness protocol */
-#endif
 };
 
 /*
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index eec8a2052da2..354b903b3a28 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -62,9 +62,7 @@
 #include "dfs_cache.h"
 #endif
 #include "fs_context.h"
-#ifdef CONFIG_CIFS_SWN_UPCALL
 #include "cifs_swn.h"
-#endif
 
 extern mempool_t *cifs_req_poolp;
 extern bool disable_legacy_dialects;
@@ -314,12 +312,8 @@ cifs_reconnect(struct TCP_Server_Info *server)
 
 		mutex_lock(&server->srv_mutex);
 
-#ifdef CONFIG_CIFS_SWN_UPCALL
-		if (server->use_swn_dstaddr) {
-			server->dstaddr = server->swn_dstaddr;
-		} else {
-#endif
 
+		if (!cifs_swn_set_server_dstaddr(server)) {
 #ifdef CONFIG_CIFS_DFS_UPCALL
 			/*
 			 * Set up next DFS target server (if any) for reconnect. If DFS
@@ -328,10 +322,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 			 */
 			reconn_set_next_dfs_target(server, cifs_sb, &tgt_list, &tgt_it);
 #endif
-
-#ifdef CONFIG_CIFS_SWN_UPCALL
 		}
-#endif
 
 		if (cifs_rdma_enabled(server))
 			rc = smbd_reconnect(server);
@@ -348,9 +339,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 			if (server->tcpStatus != CifsExiting)
 				server->tcpStatus = CifsNeedNegotiate;
 			spin_unlock(&GlobalMid_Lock);
-#ifdef CONFIG_CIFS_SWN_UPCALL
-			server->use_swn_dstaddr = false;
-#endif
+			cifs_swn_reset_server_dstaddr(server);
 			mutex_unlock(&server->srv_mutex);
 		}
 	} while (server->tcpStatus == CifsNeedReconnect);
@@ -415,10 +404,8 @@ cifs_echo_request(struct work_struct *work)
 		cifs_dbg(FYI, "Unable to send echo request to server: %s\n",
 			 server->hostname);
 
-#ifdef CONFIG_CIFS_SWN_UPCALL
 	/* Check witness registrations */
 	cifs_swn_check();
-#endif
 
 requeue_echo:
 	queue_delayed_work(cifsiod_wq, &server->echo, server->echo_interval);
@@ -1994,7 +1981,6 @@ cifs_put_tcon(struct cifs_tcon *tcon)
 		return;
 	}
 
-#ifdef CONFIG_CIFS_SWN_UPCALL
 	if (tcon->use_witness) {
 		int rc;
 
@@ -2004,7 +1990,6 @@ cifs_put_tcon(struct cifs_tcon *tcon)
 					__func__, rc);
 		}
 	}
-#endif
 
 	list_del_init(&tcon->tcon_list);
 	spin_unlock(&cifs_tcp_ses_lock);
@@ -2166,9 +2151,9 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb3_fs_context *ctx)
 		}
 		tcon->use_resilient = true;
 	}
-#ifdef CONFIG_CIFS_SWN_UPCALL
+
 	tcon->use_witness = false;
-	if (ctx->witness) {
+	if (IS_ENABLED(CONFIG_CIFS_SWN_UPCALL) && ctx->witness) {
 		if (ses->server->vals->protocol_id >= SMB30_PROT_ID) {
 			if (tcon->capabilities & SMB2_SHARE_CAP_CLUSTER) {
 				/*
@@ -2194,7 +2179,6 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb3_fs_context *ctx)
 			goto out_fail;
 		}
 	}
-#endif
 
 	/* If the user really knows what they are doing they can override */
 	if (tcon->share_flags & SMB2_SHAREFLAG_NO_CACHING) {
@@ -3862,9 +3846,7 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, kuid_t fsuid)
 	ctx->sectype = master_tcon->ses->sectype;
 	ctx->sign = master_tcon->ses->sign;
 	ctx->seal = master_tcon->seal;
-#ifdef CONFIG_CIFS_SWN_UPCALL
 	ctx->witness = master_tcon->use_witness;
-#endif
 
 	rc = cifs_set_vol_auth(ctx, master_tcon->ses);
 	if (rc) {
-- 
2.30.0