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Commit 989782dc authored by David Howells's avatar David Howells
Browse files

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: default avatarDavid Howells <dhowells@redhat.com>
parent be080a6f

fs/afs/cell.c

+634 −282

File changed.

Preview size limit exceeded, changes collapsed.

fs/afs/internal.h

+45 −15
Original line number Diff line number Diff line
@@ -207,13 +207,14 @@ struct afs_net { 
	atomic_t		nr_superblocks;



	/* Cell database */

	struct list_head	cells;

	struct rb_root		cells;

	struct afs_cell		*ws_cell;

	rwlock_t		cells_lock;

	struct rw_semaphore	cells_sem;

	wait_queue_head_t	cells_freeable_wq;

	struct work_struct	cells_manager;

	struct timer_list	cells_timer;

	atomic_t		cells_outstanding;

	seqlock_t		cells_lock;



	struct rw_semaphore	proc_cells_sem;

	spinlock_t		proc_cells_lock;

	struct list_head	proc_cells;



	/* Volume location database */
@@ -242,14 +243,26 @@ struct afs_net { 


extern struct afs_net __afs_net;// Dummy AFS network namespace; TODO: replace with real netns



enum afs_cell_state {

	AFS_CELL_UNSET,

	AFS_CELL_ACTIVATING,

	AFS_CELL_ACTIVE,

	AFS_CELL_DEACTIVATING,

	AFS_CELL_INACTIVE,

	AFS_CELL_FAILED,

};



/*

 * AFS cell record

 */

struct afs_cell {

	atomic_t		usage;

	struct list_head	link;		/* main cell list link */

	struct afs_net		*net;		/* The network namespace */

	union {

		struct rcu_head	rcu;

		struct rb_node	net_node;	/* Node in net->cells */

	};

	struct afs_net		*net;

	struct key		*anonymous_key;	/* anonymous user key for this cell */

	struct work_struct	manager;	/* Manager for init/deinit/dns */

	struct list_head	proc_link;	/* /proc cell list link */

#ifdef CONFIG_AFS_FSCACHE

	struct fscache_cookie	*cache;		/* caching cookie */
@@ -262,12 +275,26 @@ struct afs_cell { 
	/* volume location record management */

	struct rw_semaphore	vl_sem;		/* volume management serialisation semaphore */

	struct list_head	vl_list;	/* cell's active VL record list */

	time64_t		dns_expiry;	/* Time AFSDB/SRV record expires */

	time64_t		last_inactive;	/* Time of last drop of usage count */

	atomic_t		usage;

	unsigned long		flags;

#define AFS_CELL_FL_NOT_READY	0		/* The cell record is not ready for use */

#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 */

	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 */



	char			name[0];	/* cell name - must go last */

	u8			name_len;	/* Length of name */

	char			name[64 + 1];	/* Cell name, case-flattened and NUL-padded */

};



/*
@@ -500,11 +527,14 @@ static inline struct afs_cell *afs_get_cell(struct afs_cell *cell) 
		atomic_inc(&cell->usage);

	return cell;

}

extern int afs_cell_init(struct afs_net *, char *);

extern struct afs_cell *afs_cell_create(struct afs_net *, const char *, unsigned, char *, bool);

extern struct afs_cell *afs_cell_lookup(struct afs_net *, const char *, unsigned, bool);

extern struct afs_cell *afs_grab_cell(struct afs_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 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 *);

extern void __net_exit afs_cell_purge(struct afs_net *);



/*

fs/afs/main.c

+11 −5
Original line number Diff line number Diff line
@@ -46,12 +46,15 @@ static int __net_init afs_net_init(struct afs_net *net) 


	INIT_WORK(&net->charge_preallocation_work, afs_charge_preallocation);

	mutex_init(&net->socket_mutex);

	INIT_LIST_HEAD(&net->cells);

	rwlock_init(&net->cells_lock);

	init_rwsem(&net->cells_sem);

	init_waitqueue_head(&net->cells_freeable_wq);

	init_rwsem(&net->proc_cells_sem);



	net->cells = RB_ROOT;

	seqlock_init(&net->cells_lock);

	INIT_WORK(&net->cells_manager, afs_manage_cells);

	timer_setup(&net->cells_timer, afs_cells_timer, 0);



	spin_lock_init(&net->proc_cells_lock);

	INIT_LIST_HEAD(&net->proc_cells);



	INIT_LIST_HEAD(&net->vl_updates);

	INIT_LIST_HEAD(&net->vl_graveyard);

	INIT_DELAYED_WORK(&net->vl_reaper, afs_vlocation_reaper);
@@ -83,11 +86,14 @@ static int __net_init afs_net_init(struct afs_net *net) 
	return 0;



error_open_socket:

	net->live = false;

	afs_vlocation_purge(net);

	afs_cell_purge(net);

error_cell_init:

	net->live = false;

	afs_proc_cleanup(net);

error_proc:

	net->live = false;

	return ret;

}

fs/afs/proc.c

+6 −9
Original line number Diff line number Diff line
@@ -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)

fs/afs/super.c

+7 −5
Original line number Diff line number Diff line
@@ -200,10 +200,11 @@ static int afs_parse_options(struct afs_mount_params *params, 
		token = match_token(p, afs_options_list, args);

		switch (token) {

		case afs_opt_cell:

			cell = afs_cell_lookup(params->net,

			rcu_read_lock();

			cell = afs_lookup_cell_rcu(params->net,

						   args[0].from,

					       args[0].to - args[0].from,

					       false);

						   args[0].to - args[0].from);

			rcu_read_unlock();

			if (IS_ERR(cell))

				return PTR_ERR(cell);

			afs_put_cell(params->net, params->cell);
@@ -308,7 +309,8 @@ static int afs_parse_device_name(struct afs_mount_params *params, 


	/* lookup the cell record */

	if (cellname || !params->cell) {

		cell = afs_cell_lookup(params->net, cellname, cellnamesz, true);

		cell = afs_lookup_cell(params->net, cellname, cellnamesz,

				       NULL, false);

		if (IS_ERR(cell)) {

			printk(KERN_ERR "kAFS: unable to lookup cell '%*.*s'\n",

			       cellnamesz, cellnamesz, cellname ?: "");