cifs: add routines to build sessions and tcons on the fly

This patch is rather large, but it's a bit difficult to do piecemeal...

For non-multiuser mounts, everything will basically work as it does
today. A call to cifs_sb_tlink will return the "master" tcon link.

Turn the tcon pointer in the cifs_sb into a radix tree that uses the
fsuid of the process as a key. The value is a new "tcon_link" struct
that contains info about a tcon that's under construction.

When a new process needs a tcon, it'll call cifs_sb_tcon. That will
then look up the tcon_link in the radix tree. If it exists and is
valid, it's returned.

If it doesn't exist, then we stuff a new tcon_link into the tree and
mark it as pending and then go and try to build the session/tcon.
If that works, the tcon pointer in the tcon_link is updated and the
pending flag is cleared.

If the construction fails, then we set the tcon pointer to an ERR_PTR
and clear the pending flag.

If the radix tree is searched and the tcon_link is marked pending
then we go to sleep and wait for the pending flag to be cleared.

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

fs/cifs/cifs_fs_sb.h

@@ -15,6 +15,8 @@
  *   the GNU Lesser General Public License for more details.
  *
  */
+#include <linux/radix-tree.h>
+
 #ifndef _CIFS_FS_SB_H
 #define _CIFS_FS_SB_H
 
@@ -40,8 +42,9 @@
 #define CIFS_MOUNT_MULTIUSER	0x20000 /* multiuser mount */
 
 struct cifs_sb_info {
-	struct cifsTconInfo *ptcon;	/* primary mount */
-	struct list_head nested_tcon_q;
+	struct radix_tree_root tlink_tree;
+#define CIFS_TLINK_MASTER_TAG		0	/* is "master" (mount) tcon */
+	spinlock_t tlink_tree_lock;
 	struct nls_table *local_nls;
 	unsigned int rsize;
 	unsigned int wsize;

fs/cifs/cifsglob.h

@@ -317,42 +317,36 @@ struct cifsTconInfo {
  * "get" on the container.
  */
 struct tcon_link {
-	spinlock_t		tl_lock;
-	u32			tl_count;
-	u64			tl_time;
+	unsigned long		tl_index;
+	unsigned long		tl_flags;
+#define TCON_LINK_MASTER	0
+#define TCON_LINK_PENDING	1
+#define TCON_LINK_IN_TREE	2
+	unsigned long		tl_time;
+	atomic_t		tl_count;
 	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;
-}
+extern struct tcon_link *cifs_sb_tlink(struct cifs_sb_info *cifs_sb);
 
 static inline struct cifsTconInfo *
 tlink_tcon(struct tcon_link *tlink)
 {
-	return (struct cifsTconInfo *)tlink;
+	return tlink->tl_tcon;
 }
 
-static inline void
-cifs_put_tlink(struct tcon_link *tlink)
-{
-	return;
-}
+extern void cifs_put_tlink(struct tcon_link *tlink);
 
 static inline struct tcon_link *
 cifs_get_tlink(struct tcon_link *tlink)
 {
+	if (tlink && !IS_ERR(tlink))
+		atomic_inc(&tlink->tl_count);
 	return tlink;
 }
 
 /* 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;
-}
+extern struct cifsTconInfo *cifs_sb_master_tcon(struct cifs_sb_info *cifs_sb);
 
 /*
  * This info hangs off the cifsFileInfo structure, pointed to by llist.