afs: Overhaul cell database management

Overhaul the way that the in-kernel AFS client keeps track of cells in the
following manner:

 (1) Cells are now held in an rbtree to make walking them quicker and RCU
     managed (though this is probably overkill).

 (2) Cells now have a manager work item that:

     (A) Looks after fetching and refreshing the VL server list.

     (B) Manages cell record lifetime, including initialising and
     	 destruction.

     (B) Manages cell record caching whereby threads are kept around for a
     	 certain time after last use and then destroyed.

     (C) Manages the FS-Cache index cookie for a cell.  It is not permitted
     	 for a cookie to be in use twice, so we have to be careful to not
     	 allow a new cell record to exist at the same time as an old record
     	 of the same name.

 (3) Each AFS network namespace is given a manager work item that manages
     the cells within it, maintaining a single timer to prod cells into
     updating their DNS records.

     This uses the reduce_timer() facility to make the timer expire at the
     soonest timed event that needs happening.

 (4) When a module is being unloaded, cells and cell managers are now
     counted out using dec_after_work() to make sure the module text is
     pinned until after the data structures have been cleaned up.

 (5) Each cell's VL server list is now protected by a seqlock rather than a
     semaphore.

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

1 files changed, 6 insertions, 9 deletions

diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index d00d550ff2ef..08565429615d 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -186,7 +186,7 @@ static void *afs_proc_cells_start(struct seq_file *m, loff_t *_pos)
 {
 	struct afs_net *net = afs_seq2net(m);
 
-	down_read(&net->proc_cells_sem);
+	rcu_read_lock();
 	return seq_list_start_head(&net->proc_cells, *_pos);
 }
 
@@ -205,9 +205,7 @@ static void *afs_proc_cells_next(struct seq_file *m, void *v, loff_t *pos)
  */
 static void afs_proc_cells_stop(struct seq_file *m, void *v)
 {
-	struct afs_net *net = afs_seq2net(m);
-
-	up_read(&net->proc_cells_sem);
+	rcu_read_unlock();
 }
 
 /*
@@ -225,8 +223,7 @@ static int afs_proc_cells_show(struct seq_file *m, void *v)
 	}
 
 	/* display one cell per line on subsequent lines */
-	seq_printf(m, "%3d %s\n",
-		   atomic_read(&cell->usage), cell->name);
+	seq_printf(m, "%3u %s\n", atomic_read(&cell->usage), cell->name);
 	return 0;
 }
 
@@ -279,13 +276,13 @@ static ssize_t afs_proc_cells_write(struct file *file, const char __user *buf,
 	if (strcmp(kbuf, "add") == 0) {
 		struct afs_cell *cell;
 
-		cell = afs_cell_create(net, name, strlen(name), args, false);
+		cell = afs_lookup_cell(net, name, strlen(name), args, true);
 		if (IS_ERR(cell)) {
 			ret = PTR_ERR(cell);
 			goto done;
 		}
 
-		afs_put_cell(net, cell);
+		set_bit(AFS_CELL_FL_NO_GC, &cell->flags);
 		printk("kAFS: Added new cell '%s'\n", name);
 	} else {
 		goto inval;
@@ -354,7 +351,7 @@ int afs_proc_cell_setup(struct afs_net *net, struct afs_cell *cell)
 {
 	struct proc_dir_entry *dir;
 
-	_enter("%p{%s}", cell, cell->name);
+	_enter("%p{%s},%p", cell, cell->name, net->proc_afs);
 
 	dir = proc_mkdir(cell->name, net->proc_afs);
 	if (!dir)