cifs: add refcounted and timestamped container for holding tcons

Eventually, we'll need to track the use of tcons on a per-sb basis, so that
we know when it's ok to tear them down. Begin this conversion by adding a
new "tcon_link" struct and accessors that get it. For now, the core data
structures are untouched -- cifs_sb still just points to a single tcon and
the pointers are just cast to deal with the accessor functions. A later
patch will flesh this out.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 38 insertions, 13 deletions

diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index c265ebdcd177..cdfd2db4e70d 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -311,6 +311,44 @@ struct cifsTconInfo {
 };
 
 /*
+ * This is a refcounted and timestamped container for a tcon pointer. The
+ * container holds a tcon reference. It is considered safe to free one of
+ * these when the tl_count goes to 0. The tl_time is the time of the last
+ * "get" on the container.
+ */
+struct tcon_link {
+	spinlock_t		tl_lock;
+	u32			tl_count;
+	u64			tl_time;
+	struct cifsTconInfo	*tl_tcon;
+};
+
+static inline struct tcon_link *
+cifs_sb_tlink(struct cifs_sb_info *cifs_sb)
+{
+	return (struct tcon_link *)cifs_sb->ptcon;
+}
+
+static inline struct cifsTconInfo *
+tlink_tcon(struct tcon_link *tlink)
+{
+	return (struct cifsTconInfo *)tlink;
+}
+
+static inline void
+cifs_put_tlink(struct tcon_link *tlink)
+{
+	return;
+}
+
+/* This function is always expected to succeed */
+static inline struct cifsTconInfo *
+cifs_sb_master_tcon(struct cifs_sb_info *cifs_sb)
+{
+	return cifs_sb->ptcon;
+}
+
+/*
  * This info hangs off the cifsFileInfo structure, pointed to by llist.
  * This is used to track byte stream locks on the file
  */
@@ -413,19 +451,6 @@ CIFS_SB(struct super_block *sb)
 	return sb->s_fs_info;
 }
 
-static inline struct cifsTconInfo *
-cifs_sb_tcon(struct cifs_sb_info *cifs_sb)
-{
-	return cifs_sb->ptcon;
-}
-
-/* This function is always expected to succeed */
-static inline struct cifsTconInfo *
-cifs_sb_master_tcon(struct cifs_sb_info *cifs_sb)
-{
-	return cifs_sb->ptcon;
-}
-
 static inline char CIFS_DIR_SEP(const struct cifs_sb_info *cifs_sb)
 {
 	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS)