cifs: store pointer to master tlink in superblock (try #2)

This is the second version of this patch, the only difference between
it and the first one is that this explicitly makes cifs_sb_master_tlink
a static inline.

Instead of keeping a tag on the master tlink in the tree, just keep a
pointer to the master in the superblock. That eliminates the need for
using the radix tree to look up a tagged entry.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Signed-off-by: NSteve French <sfrench@us.ibm.com>

fs/cifs/cifs_fs_sb.h

@@ -43,8 +43,8 @@
 
 struct cifs_sb_info {
 	struct radix_tree_root tlink_tree;
-#define CIFS_TLINK_MASTER_TAG		0	/* is "master" (mount) tcon */
 	spinlock_t tlink_tree_lock;
+	struct tcon_link *master_tlink;
 	struct nls_table *local_nls;
 	unsigned int rsize;
 	unsigned int wsize;

fs/cifs/connect.c

@@ -2914,11 +2914,11 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
 
 	spin_lock(&cifs_sb->tlink_tree_lock);
 	radix_tree_insert(&cifs_sb->tlink_tree, pSesInfo->linux_uid, tlink);
-	radix_tree_tag_set(&cifs_sb->tlink_tree, pSesInfo->linux_uid,
-			   CIFS_TLINK_MASTER_TAG);
 	spin_unlock(&cifs_sb->tlink_tree_lock);
 	radix_tree_preload_end();
 
+	cifs_sb->master_tlink = tlink;
+
 	queue_delayed_work(system_nrt_wq, &cifs_sb->prune_tlinks,
 				TLINK_IDLE_EXPIRE);
 
@@ -3271,22 +3271,10 @@ cifs_construct_tcon(struct cifs_sb_info *cifs_sb, uid_t fsuid)
 	return tcon;
 }
 
-static struct tcon_link *
+static inline struct tcon_link *
 cifs_sb_master_tlink(struct cifs_sb_info *cifs_sb)
 {
-	struct tcon_link *tlink;
-	unsigned int ret;
-
-	spin_lock(&cifs_sb->tlink_tree_lock);
-	ret = radix_tree_gang_lookup_tag(&cifs_sb->tlink_tree, (void **)&tlink,
-					0, 1, CIFS_TLINK_MASTER_TAG);
-	spin_unlock(&cifs_sb->tlink_tree_lock);
-
-	/* the master tcon should always be present */
-	if (ret == 0)
-		BUG();
-
-	return tlink;
+	return cifs_sb->master_tlink;
 }
 
 struct cifsTconInfo *