From fe4734d01989e7f03d5d781687fa4962d965b662 Mon Sep 17 00:00:00 2001
From: Zach Brown <zab@versity.com>
Date: Fri, 9 Dec 2022 15:39:10 -0800
Subject: [PATCH] Save a full stable super in the server

The server has a mechanism for tracking the last stable roots used by
network rpcs.  We expand it a bit to include the entire super so
that we can add users in the server which want the last full stable
super.  We can still use the stable super to give out the stable
roots.

Signed-off-by: Zach Brown <zab@versity.com>
---
 kmod/src/server.c | 45 ++++++++++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/kmod/src/server.c b/kmod/src/server.c
index 8ce503c1..bd76cec1 100644
--- a/kmod/src/server.c
+++ b/kmod/src/server.c
@@ -130,9 +130,9 @@ struct server_info {
 	struct mutex srch_mutex;
 	struct mutex mounted_clients_mutex;
 
-	/* stable versions stored from commits, given in locks and rpcs */
-	seqcount_t roots_seqcount;
-	struct scoutfs_net_roots roots;
+	/* stable super stored from commits, given in locks and rpcs */
+	seqcount_t stable_seqcount;
+	struct scoutfs_super_block stable_super;
 
 	/* serializing and get and set volume options */
 	seqcount_t volopt_seqcount;
@@ -469,16 +469,22 @@ static void commit_end(struct super_block *sb, struct commit_users *cusers, int
 	wake_up(&cusers->waitq);
 }
 
-static void get_roots(struct super_block *sb,
-			      struct scoutfs_net_roots *roots)
+static void get_stable(struct super_block *sb, struct scoutfs_super_block *super,
+		       struct scoutfs_net_roots *roots)
 {
 	DECLARE_SERVER_INFO(sb, server);
 	unsigned int seq;
 
 	do {
-		seq = read_seqcount_begin(&server->roots_seqcount);
-		*roots = server->roots;
-	} while (read_seqcount_retry(&server->roots_seqcount, seq));
+		seq = read_seqcount_begin(&server->stable_seqcount);
+		if (super)
+			*super = server->stable_super;
+		if (roots) {
+			roots->fs_root = server->stable_super.fs_root;
+			roots->logs_root = server->stable_super.logs_root;
+			roots->srch_root = server->stable_super.srch_root;
+		}
+	} while (read_seqcount_retry(&server->stable_seqcount, seq));
 }
 
 u64 scoutfs_server_seq(struct super_block *sb)
@@ -510,17 +516,12 @@ void scoutfs_server_set_seq_if_greater(struct super_block *sb, u64 seq)
 	}
 }
 
-static void set_roots(struct server_info *server,
-		      struct scoutfs_btree_root *fs_root,
-		      struct scoutfs_btree_root *logs_root,
-		      struct scoutfs_btree_root *srch_root)
+static void set_stable_super(struct server_info *server, struct scoutfs_super_block *super)
 {
 	preempt_disable();
-	write_seqcount_begin(&server->roots_seqcount);
-	server->roots.fs_root = *fs_root;
-	server->roots.logs_root = *logs_root;
-	server->roots.srch_root = *srch_root;
-	write_seqcount_end(&server->roots_seqcount);
+	write_seqcount_begin(&server->stable_seqcount);
+	server->stable_super = *super;
+	write_seqcount_end(&server->stable_seqcount);
 	preempt_enable();
 }
 
@@ -603,8 +604,7 @@ static void scoutfs_server_commit_func(struct work_struct *work)
 		goto out;
 	}
 
-	set_roots(server, &super->fs_root, &super->logs_root,
-		  &super->srch_root);
+	set_stable_super(server, super);
 
 	/* swizzle the active and idle server alloc/freed heads */
 	server->other_ind ^= 1;
@@ -1624,7 +1624,7 @@ static int server_get_roots(struct super_block *sb,
 		memset(&roots, 0, sizeof(roots));
 		ret = -EINVAL;
 	}  else {
-		get_roots(sb, &roots);
+		get_stable(sb, NULL, &roots);
 		ret = 0;
 	}
 
@@ -4230,8 +4230,7 @@ static void scoutfs_server_worker(struct work_struct *work)
 	write_seqcount_end(&server->volopt_seqcount);
 
 	atomic64_set(&server->seq_atomic, le64_to_cpu(super->seq));
-	set_roots(server, &super->fs_root, &super->logs_root,
-		  &super->srch_root);
+	set_stable_super(server, super);
 
 	/* prepare server alloc for this transaction, larger first */
 	if (le64_to_cpu(super->server_meta_avail[0].total_nr) <
@@ -4381,7 +4380,7 @@ int scoutfs_server_setup(struct super_block *sb)
 	INIT_WORK(&server->log_merge_free_work, server_log_merge_free_work);
 	mutex_init(&server->srch_mutex);
 	mutex_init(&server->mounted_clients_mutex);
-	seqcount_init(&server->roots_seqcount);
+	seqcount_init(&server->stable_seqcount);
 	seqcount_init(&server->volopt_seqcount);
 	mutex_init(&server->volopt_mutex);
 	INIT_WORK(&server->fence_pending_recov_work, fence_pending_recov_worker);