Message-ID: <20231109154004.3317227-38-dhowells@redhat.com>
Date:   Thu,  9 Nov 2023 15:40:00 +0000
From:   David Howells <dhowells@...hat.com>
To:     Marc Dionne <marc.dionne@...istor.com>
Cc:     David Howells <dhowells@...hat.com>, linux-afs@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 37/41] 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@...hat.com>
cc: Marc Dionne <marc.dionne@...istor.com>
cc: linux-afs@...ts.infradead.org
---
 fs/afs/callback.c          | 33 +++++++++++++++++++--------------
 fs/afs/cell.c              |  2 +-
 fs/afs/internal.h          |  6 +++---
 fs/afs/server.c            |  2 --
 fs/afs/server_list.c       | 22 +++++++++++-----------
 fs/afs/volume.c            | 15 +++++++++++++++
 include/trace/events/afs.h |  2 ++
 7 files changed, 51 insertions(+), 31 deletions(-)

diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index a484fa642808..535477f88a4f 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 = 0;
 
-	do {
+	for (;;) {
 		/* Unfortunately, rbtree walking doesn't give reliable results
 		 * under just the RCU read lock, so we have to check for
 		 * changes.
@@ -132,7 +135,12 @@ 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;
@@ -187,12 +195,11 @@ 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 }",
@@ -206,6 +213,9 @@ static void afs_break_some_callbacks(struct afs_server *server,
 			*residue++ = *cbb;
 		}
 	}
+
+	rcu_read_unlock();
+	afs_put_volume(volume, afs_volume_trace_put_callback);
 }
 
 /*
@@ -218,11 +228,6 @@ 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 6b389f2bcd0c..1e5cb0f6ee07 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 0a4ecfc250bf..73f0a456ab98 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;
@@ -1040,7 +1039,6 @@ 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);
@@ -1619,6 +1617,8 @@ extern struct afs_volume *afs_get_volume(struct afs_volume *, enum afs_volume_tr
 void afs_put_volume(struct afs_volume *volume, enum afs_volume_trace reason);
 extern int afs_check_volume_status(struct afs_volume *, struct afs_operation *);
 
+bool afs_try_get_volume(struct afs_volume *volume, enum afs_volume_trace reason);
+
 /*
  * write.c
  */
diff --git a/fs/afs/server.c b/fs/afs/server.c
index 811dbda88f9c..c97617366557 100644
--- a/fs/afs/server.c
+++ b/fs/afs/server.c
@@ -217,7 +217,6 @@ 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);
@@ -469,7 +468,6 @@ 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);
 }
diff --git a/fs/afs/volume.c b/fs/afs/volume.c
index 1d3bd14dfa2f..00253032ccca 100644
--- a/fs/afs/volume.c
+++ b/fs/afs/volume.c
@@ -242,6 +242,21 @@ static void afs_destroy_volume(struct work_struct *work)
 	_leave(" [destroyed]");
 }
 
+
+/*
+ * Try to get a reference on a volume record.
+ */
+bool afs_try_get_volume(struct afs_volume *volume, enum afs_volume_trace reason)
+{
+	int r;
+
+	if (__refcount_inc_not_zero(&volume->ref, &r)) {
+		trace_afs_volume(volume->vid, r + 1, reason);
+		return true;
+	}
+	return false;
+}
+
 /*
  * Get a reference on a volume record.
  */
diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h
index cf2fa4fddd5b..63ab23876be8 100644
--- a/include/trace/events/afs.h
+++ b/include/trace/events/afs.h
@@ -151,9 +151,11 @@ enum yfs_cm_operation {
 	EM(afs_volume_trace_alloc,		"ALLOC         ") \
 	EM(afs_volume_trace_free,		"FREE          ") \
 	EM(afs_volume_trace_get_alloc_sbi,	"GET sbi-alloc ") \
+	EM(afs_volume_trace_get_callback,	"GET callback  ") \
 	EM(afs_volume_trace_get_cell_insert,	"GET cell-insrt") \
 	EM(afs_volume_trace_get_new_op,		"GET op-new    ") \
 	EM(afs_volume_trace_get_query_alias,	"GET cell-alias") \
+	EM(afs_volume_trace_put_callback,	"PUT callback  ") \
 	EM(afs_volume_trace_put_cell_dup,	"PUT cell-dup  ") \
 	EM(afs_volume_trace_put_cell_root,	"PUT cell-root ") \
 	EM(afs_volume_trace_put_destroy_sbi,	"PUT sbi-destry") \

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