afs: Apply server breaks to mmap'd files in the call processor

Apply server breaks to mmap'd files that are being used from that server
from the call processor work function rather than punting it off to a
workqueue.  The work item, afs_server_init_callback(), then bumps each
individual inode off to its own work item introducing a potentially lengthy
delay.  This reduces that delay at the cost of extending the amount of time
we delay replying to the CB.InitCallBack3 notification RPC from the server.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org

5 files changed, 32 insertions, 31 deletions

diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 90f9b2a46ff4..f67e88076761 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -33,9 +33,8 @@ void afs_invalidate_mmap_work(struct work_struct *work)
 	unmap_mapping_pages(vnode->netfs.inode.i_mapping, 0, 0, false);
 }
 
-void afs_server_init_callback_work(struct work_struct *work)
+static void afs_server_init_callback(struct afs_server *server)
 {
-	struct afs_server *server = container_of(work, struct afs_server, initcb_work);
 	struct afs_vnode *vnode;
 	struct afs_cell *cell = server->cell;
 
@@ -57,15 +56,19 @@ void afs_server_init_callback_work(struct work_struct *work)
  */
 void afs_init_callback_state(struct afs_server *server)
 {
-	rcu_read_lock();
+	struct afs_cell *cell = server->cell;
+
+	down_read(&cell->vs_lock);
+
 	do {
 		server->cb_s_break++;
 		atomic_inc(&server->cell->fs_s_break);
 		if (!list_empty(&server->cell->fs_open_mmaps))
-			queue_work(system_unbound_wq, &server->initcb_work);
+			afs_server_init_callback(server);
 
 	} while ((server = rcu_dereference(server->uuid_next)));
-	rcu_read_unlock();
+
+	up_read(&cell->vs_lock);
 }
 
 /*
@@ -112,7 +115,7 @@ static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell *cell,
 	struct rb_node *p;
 	int seq = 1;
 
-	do {
+	for (;;) {
 		/* Unfortunately, rbtree walking doesn't give reliable results
 		 * under just the RCU read lock, so we have to check for
 		 * changes.
@@ -133,7 +136,12 @@ static struct afs_volume *afs_lookup_volume_rcu(struct afs_cell *cell,
 			volume = NULL;
 		}
 
-	} while (need_seqretry(&cell->volume_lock, seq));
+		if (volume && afs_try_get_volume(volume, afs_volume_trace_get_callback))
+			break;
+		if (!need_seqretry(&cell->volume_lock, seq))
+			break;
+		seq |= 1; /* Want a lock next time */
+	}
 
 	done_seqretry(&cell->volume_lock, seq);
 	return volume;
@@ -188,12 +196,11 @@ static void afs_break_some_callbacks(struct afs_server *server,
 	afs_volid_t vid = cbb->fid.vid;
 	size_t i;
 
+	rcu_read_lock();
 	volume = afs_lookup_volume_rcu(server->cell, vid);
-
 	/* TODO: Find all matching volumes if we couldn't match the server and
 	 * break them anyway.
 	 */
-
 	for (i = *_count; i > 0; cbb++, i--) {
 		if (cbb->fid.vid == vid) {
 			_debug("- Fid { vl=%08llx n=%llu u=%u }",
@@ -207,6 +214,9 @@ static void afs_break_some_callbacks(struct afs_server *server,
 			*residue++ = *cbb;
 		}
 	}
+
+	rcu_read_unlock();
+	afs_put_volume(volume, afs_volume_trace_put_callback);
 }
 
 /*
@@ -219,11 +229,6 @@ void afs_break_callbacks(struct afs_server *server, size_t count,
 
 	ASSERT(server != NULL);
 
-	rcu_read_lock();
-
 	while (count > 0)
 		afs_break_some_callbacks(server, callbacks, &count);
-
-	rcu_read_unlock();
-	return;
 }
diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 55ee194e31ff..e4b6a80763d7 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -161,7 +161,7 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 	refcount_set(&cell->ref, 1);
 	atomic_set(&cell->active, 0);
 	INIT_WORK(&cell->manager, afs_manage_cell_work);
-	spin_lock_init(&cell->vs_lock);
+	init_rwsem(&cell->vs_lock);
 	cell->volumes = RB_ROOT;
 	INIT_HLIST_HEAD(&cell->proc_volumes);
 	seqlock_init(&cell->volume_lock);
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 4a3d946b1d2a..5ae4ca999d65 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -414,7 +414,7 @@ struct afs_cell {
 	unsigned int		debug_id;
 
 	/* The volumes belonging to this cell */
-	spinlock_t		vs_lock;	/* Lock for server->volumes */
+	struct rw_semaphore	vs_lock;	/* Lock for server->volumes */
 	struct rb_root		volumes;	/* Tree of volumes on this server */
 	struct hlist_head	proc_volumes;	/* procfs volume list */
 	seqlock_t		volume_lock;	/* For volumes */
@@ -566,7 +566,6 @@ struct afs_server {
 	struct hlist_node	addr6_link;	/* Link in net->fs_addresses6 */
 	struct hlist_node	proc_link;	/* Link in net->fs_proc */
 	struct list_head	volumes;	/* RCU list of afs_server_entry objects */
-	struct work_struct	initcb_work;	/* Work for CB.InitCallBackState* */
 	struct afs_server	*gc_next;	/* Next server in manager's list */
 	time64_t		unuse_time;	/* Time at which last unused */
 	unsigned long		flags;
@@ -1041,7 +1040,6 @@ void afs_get_address_preferences(struct afs_net *net, struct afs_addr_list *alis
  * callback.c
  */
 extern void afs_invalidate_mmap_work(struct work_struct *);
-extern void afs_server_init_callback_work(struct work_struct *work);
 extern void afs_init_callback_state(struct afs_server *);
 extern void __afs_break_callback(struct afs_vnode *, enum afs_cb_break_reason);
 extern void afs_break_callback(struct afs_vnode *, enum afs_cb_break_reason);
diff --git a/fs/afs/server.c b/fs/afs/server.c
index db2f66b11b40..e169121f603e 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -218,7 +218,6 @@ static struct afs_server *afs_alloc_server(struct afs_cell *cell,
 	server->uuid = *uuid;
 	rwlock_init(&server->fs_lock);
 	INIT_LIST_HEAD(&server->volumes);
-	INIT_WORK(&server->initcb_work, afs_server_init_callback_work);
 	init_waitqueue_head(&server->probe_wq);
 	INIT_LIST_HEAD(&server->probe_link);
 	spin_lock_init(&server->probe_lock);
@@ -470,7 +469,6 @@ static void afs_destroy_server(struct afs_net *net, struct afs_server *server)
 	if (test_bit(AFS_SERVER_FL_MAY_HAVE_CB, &server->flags))
 		afs_give_up_callbacks(net, server);
 
-	flush_work(&server->initcb_work);
 	afs_put_server(net, server, afs_server_trace_destroy);
 }
 
diff --git a/fs/afs/server_list.c b/fs/afs/server_list.c
index 4d6369477f54..cfd900eb09ed 100644
--- a/fs/afs/server_list.c
+++ b/fs/afs/server_list.c
@@ -136,7 +136,7 @@ void afs_attach_volume_to_servers(struct afs_volume *volume, struct afs_server_l
 	struct list_head *p;
 	unsigned int i;
 
-	spin_lock(&volume->cell->vs_lock);
+	down_write(&volume->cell->vs_lock);
 
 	for (i = 0; i < slist->nr_servers; i++) {
 		se = &slist->servers[i];
@@ -147,11 +147,11 @@ void afs_attach_volume_to_servers(struct afs_volume *volume, struct afs_server_l
 			if (volume->vid <= pe->volume->vid)
 				break;
 		}
-		list_add_tail_rcu(&se->slink, p);
+		list_add_tail(&se->slink, p);
 	}
 
 	slist->attached = true;
-	spin_unlock(&volume->cell->vs_lock);
+	up_write(&volume->cell->vs_lock);
 }
 
 /*
@@ -164,7 +164,7 @@ void afs_reattach_volume_to_servers(struct afs_volume *volume, struct afs_server
 {
 	unsigned int n = 0, o = 0;
 
-	spin_lock(&volume->cell->vs_lock);
+	down_write(&volume->cell->vs_lock);
 
 	while (n < new->nr_servers || o < old->nr_servers) {
 		struct afs_server_entry *pn = n < new->nr_servers ? &new->servers[n] : NULL;
@@ -174,7 +174,7 @@ void afs_reattach_volume_to_servers(struct afs_volume *volume, struct afs_server
 		int diff;
 
 		if (pn && po && pn->server == po->server) {
-			list_replace_rcu(&po->slink, &pn->slink);
+			list_replace(&po->slink, &pn->slink);
 			n++;
 			o++;
 			continue;
@@ -192,15 +192,15 @@ void afs_reattach_volume_to_servers(struct afs_volume *volume, struct afs_server
 				if (volume->vid <= s->volume->vid)
 					break;
 			}
-			list_add_tail_rcu(&pn->slink, p);
+			list_add_tail(&pn->slink, p);
 			n++;
 		} else {
-			list_del_rcu(&po->slink);
+			list_del(&po->slink);
 			o++;
 		}
 	}
 
-	spin_unlock(&volume->cell->vs_lock);
+	up_write(&volume->cell->vs_lock);
 }
 
 /*
@@ -213,11 +213,11 @@ void afs_detach_volume_from_servers(struct afs_volume *volume, struct afs_server
 	if (!slist->attached)
 		return;
 
-	spin_lock(&volume->cell->vs_lock);
+	down_write(&volume->cell->vs_lock);
 
 	for (i = 0; i < slist->nr_servers; i++)
-		list_del_rcu(&slist->servers[i].slink);
+		list_del(&slist->servers[i].slink);
 
 	slist->attached = false;
-	spin_unlock(&volume->cell->vs_lock);
+	up_write(&volume->cell->vs_lock);
 }