afs: Add an address list concept

Add an RCU replaceable address list structure to hold a list of server
addresses.  The list also holds the

To this end:

 (1) A cell's VL server address list can be loaded directly via insmod or
     echo to /proc/fs/afs/cells or dynamically from a DNS query for AFSDB
     or SRV records.

 (2) Anyone wanting to use a cell's VL server address must wait until the
     cell record comes online and has tried to obtain some addresses.

 (3) An FS server's address list, for the moment, has a single entry that
     is the key to the server list.  This will change in the future when a
     server is instead keyed on its UUID and the VL.GetAddrsU operation is
     used.

 (4) An 'address cursor' concept is introduced to handle iteration through
     the address list.  This is passed to the afs_make_call() as, in the
     future, stuff (such as abort code) that doesn't outlast the call will
     be returned in it.

In the future, we might want to annotate the list with information about
how each address fares.  We might then want to propagate such annotations
over address list replacement.

Whilst we're at it, we allow IPv6 addresses to be specified in
colon-delimited lists by enclosing them in square brackets.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 83 insertions, 37 deletions

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 51e3825..df52bf1 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -71,6 +71,17 @@ enum afs_call_state {
 };
 
 /*
+ * List of server addresses.
+ */
+struct afs_addr_list {
+	struct rcu_head		rcu;		/* Must be first */
+	refcount_t		usage;
+	unsigned short		nr_addrs;
+	unsigned short		index;		/* Address currently in use */
+	struct sockaddr_rxrpc	addrs[];
+};
+
+/*
  * a record of an in-progress RxRPC call
  */
 struct afs_call {
@@ -283,16 +294,15 @@ struct afs_cell {
 #define AFS_CELL_FL_NO_GC	1		/* The cell was added manually, don't auto-gc */
 #define AFS_CELL_FL_NOT_FOUND	2		/* Permanent DNS error */
 #define AFS_CELL_FL_DNS_FAIL	3		/* Failed to access DNS */
+#define AFS_CELL_FL_NO_LOOKUP_YET 4		/* Not completed first DNS lookup yet */
 	enum afs_cell_state	state;
 	short			error;
 
 	spinlock_t		vl_lock;	/* vl_list lock */
 
 	/* VLDB server list. */
-	seqlock_t		vl_addrs_lock;
-	unsigned short		vl_naddrs;	/* number of VL servers in addr list */
-	unsigned short		vl_curr_svix;	/* current server index */
-	struct sockaddr_rxrpc	vl_addrs[AFS_CELL_MAX_ADDRS];	/* cell VL server addresses */
+	rwlock_t		vl_addrs_lock;	/* Lock on vl_addrs */
+	struct afs_addr_list	__rcu *vl_addrs; /* List of VL servers */
 	u8			name_len;	/* Length of name */
 	char			name[64 + 1];	/* Cell name, case-flattened and NUL-padded */
 };
@@ -343,7 +353,7 @@ struct afs_vlocation {
 struct afs_server {
 	atomic_t		usage;
 	time64_t		time_of_death;	/* time at which put reduced usage to 0 */
-	struct sockaddr_rxrpc	addr;		/* server address */
+	struct afs_addr_list	__rcu *addrs;	/* List of addresses for this server */
 	struct afs_net		*net;		/* Network namespace in which the server resides */
 	struct afs_cell		*cell;		/* cell in which server resides */
 	struct list_head	link;		/* link in cell's server list */
@@ -485,8 +495,49 @@ struct afs_interface {
 	unsigned	mtu;		/* MTU of interface */
 };
 
+/*
+ * Cursor for iterating over a server's address list.
+ */
+struct afs_addr_cursor {
+	struct afs_addr_list	*alist;		/* Current address list (pins ref) */
+	struct sockaddr_rxrpc	*addr;
+	unsigned short		start;		/* Starting point in alist->addrs[] */
+	unsigned short		index;		/* Wrapping offset from start to current addr */
+	short			error;
+	bool			begun;		/* T if we've begun iteration */
+	bool			responded;	/* T if the current address responded */
+};
+
+/*
+ * Cursor for iterating over a set of fileservers.
+ */
+struct afs_fs_cursor {
+	struct afs_addr_cursor	ac;
+	struct afs_server	*server;	/* Current server (pins ref) */
+};
+
 /*****************************************************************************/
 /*
+ * addr_list.c
+ */
+static inline struct afs_addr_list *afs_get_addrlist(struct afs_addr_list *alist)
+{
+	if (alist)
+		refcount_inc(&alist->usage);
+	return alist;
+}
+extern struct afs_addr_list *afs_alloc_addrlist(unsigned int,
+						unsigned short,
+						unsigned short);
+extern void afs_put_addrlist(struct afs_addr_list *);
+extern struct afs_addr_list *afs_parse_text_addrs(const char *, size_t, char,
+						  unsigned short, unsigned short);
+extern struct afs_addr_list *afs_dns_query(struct afs_cell *, time64_t *);
+extern bool afs_iterate_addresses(struct afs_addr_cursor *);
+extern int afs_end_cursor(struct afs_addr_cursor *);
+extern int afs_set_vl_cursor(struct afs_addr_cursor *, struct afs_cell *);
+
+/*
  * cache.c
  */
 #ifdef CONFIG_AFS_FSCACHE
@@ -521,17 +572,11 @@ static inline struct afs_cb_interest *afs_get_cb_interest(struct afs_cb_interest
 /*
  * cell.c
  */
- static inline struct afs_cell *afs_get_cell(struct afs_cell *cell)
-{
-	if (cell)
-		atomic_inc(&cell->usage);
-	return cell;
-}
-
 extern int afs_cell_init(struct afs_net *, const char *);
 extern struct afs_cell *afs_lookup_cell_rcu(struct afs_net *, const char *, unsigned);
 extern struct afs_cell *afs_lookup_cell(struct afs_net *, const char *, unsigned,
 					const char *, bool);
+extern struct afs_cell *afs_get_cell(struct afs_cell *);
 extern void afs_put_cell(struct afs_net *, struct afs_cell *);
 extern void afs_manage_cells(struct work_struct *);
 extern void afs_cells_timer(struct timer_list *);
@@ -574,40 +619,41 @@ extern int afs_flock(struct file *, int, struct file_lock *);
 /*
  * fsclient.c
  */
-extern int afs_fs_fetch_file_status(struct afs_server *, struct key *,
+extern int afs_fs_fetch_file_status(struct afs_fs_cursor *, struct key *,
 				    struct afs_vnode *, struct afs_volsync *,
 				    bool);
 extern int afs_fs_give_up_callbacks(struct afs_net *, struct afs_server *, bool);
-extern int afs_fs_fetch_data(struct afs_server *, struct key *,
+extern int afs_fs_fetch_data(struct afs_fs_cursor *, struct key *,
 			     struct afs_vnode *, struct afs_read *, bool);
-extern int afs_fs_create(struct afs_server *, struct key *,
+extern int afs_fs_create(struct afs_fs_cursor *, struct key *,
 			 struct afs_vnode *, const char *, umode_t,
 			 struct afs_fid *, struct afs_file_status *,
 			 struct afs_callback *, bool);
-extern int afs_fs_remove(struct afs_server *, struct key *,
+extern int afs_fs_remove(struct afs_fs_cursor *, struct key *,
 			 struct afs_vnode *, const char *, bool, bool);
-extern int afs_fs_link(struct afs_server *, struct key *, struct afs_vnode *,
+extern int afs_fs_link(struct afs_fs_cursor *, struct key *, struct afs_vnode *,
 		       struct afs_vnode *, const char *, bool);
-extern int afs_fs_symlink(struct afs_server *, struct key *,
+extern int afs_fs_symlink(struct afs_fs_cursor *, struct key *,
 			  struct afs_vnode *, const char *, const char *,
 			  struct afs_fid *, struct afs_file_status *, bool);
-extern int afs_fs_rename(struct afs_server *, struct key *,
+extern int afs_fs_rename(struct afs_fs_cursor *, struct key *,
 			 struct afs_vnode *, const char *,
 			 struct afs_vnode *, const char *, bool);
-extern int afs_fs_store_data(struct afs_server *, struct afs_writeback *,
+extern int afs_fs_store_data(struct afs_fs_cursor *, struct afs_writeback *,
 			     pgoff_t, pgoff_t, unsigned, unsigned, bool);
-extern int afs_fs_setattr(struct afs_server *, struct key *,
+extern int afs_fs_setattr(struct afs_fs_cursor *, struct key *,
 			  struct afs_vnode *, struct iattr *, bool);
-extern int afs_fs_get_volume_status(struct afs_server *, struct key *,
+extern int afs_fs_get_volume_status(struct afs_fs_cursor *, struct key *,
 				    struct afs_vnode *,
 				    struct afs_volume_status *, bool);
-extern int afs_fs_set_lock(struct afs_server *, struct key *,
+extern int afs_fs_set_lock(struct afs_fs_cursor *, struct key *,
 			   struct afs_vnode *, afs_lock_type_t, bool);
-extern int afs_fs_extend_lock(struct afs_server *, struct key *,
+extern int afs_fs_extend_lock(struct afs_fs_cursor *, struct key *,
 			      struct afs_vnode *, bool);
-extern int afs_fs_release_lock(struct afs_server *, struct key *,
+extern int afs_fs_release_lock(struct afs_fs_cursor *, struct key *,
 			       struct afs_vnode *, bool);
-extern int afs_fs_give_up_all_callbacks(struct afs_server *, struct key *, bool);
+extern int afs_fs_give_up_all_callbacks(struct afs_server *, struct afs_addr_cursor *,
+					struct key *, bool);
 
 /*
  * inode.c
@@ -697,7 +743,7 @@ extern void __net_exit afs_close_socket(struct afs_net *);
 extern void afs_charge_preallocation(struct work_struct *);
 extern void afs_put_call(struct afs_call *);
 extern int afs_queue_call_work(struct afs_call *);
-extern long afs_make_call(struct sockaddr_rxrpc *, struct afs_call *, gfp_t, bool);
+extern long afs_make_call(struct afs_addr_cursor *, struct afs_call *, gfp_t, bool);
 extern struct afs_call *afs_alloc_flat_call(struct afs_net *,
 					    const struct afs_call_type *,
 					    size_t, size_t);
@@ -751,13 +797,11 @@ extern void __exit afs_fs_exit(void);
 /*
  * vlclient.c
  */
-extern int afs_vl_get_entry_by_name(struct afs_net *,
-				    struct sockaddr_rxrpc *, struct key *,
-				    const char *, struct afs_cache_vlocation *,
-				    bool);
-extern int afs_vl_get_entry_by_id(struct afs_net *,
-				  struct sockaddr_rxrpc *, struct key *,
-				  afs_volid_t, afs_voltype_t,
+extern int afs_vl_get_entry_by_name(struct afs_net *, struct afs_addr_cursor *,
+				    struct key *, const char *,
+				    struct afs_cache_vlocation *, bool);
+extern int afs_vl_get_entry_by_id(struct afs_net *, struct afs_addr_cursor *,
+				  struct key *, afs_volid_t, afs_voltype_t,
 				  struct afs_cache_vlocation *, bool);
 
 /*
@@ -828,9 +872,11 @@ static inline struct afs_volume *afs_get_volume(struct afs_volume *volume)
 
 extern void afs_put_volume(struct afs_cell *, struct afs_volume *);
 extern struct afs_volume *afs_volume_lookup(struct afs_mount_params *);
-extern struct afs_server *afs_volume_pick_fileserver(struct afs_vnode *);
-extern int afs_volume_release_fileserver(struct afs_vnode *,
-					 struct afs_server *, int);
+extern void afs_init_fs_cursor(struct afs_fs_cursor *, struct afs_vnode *);
+extern int afs_set_fs_cursor(struct afs_fs_cursor *, struct afs_vnode *);
+extern bool afs_volume_pick_fileserver(struct afs_fs_cursor *, struct afs_vnode *);
+extern bool afs_iterate_fs_cursor(struct afs_fs_cursor *, struct afs_vnode *);
+extern int afs_end_fs_cursor(struct afs_fs_cursor *, struct afs_net *);
 
 /*
  * write.c