Re: [RFC] write_super is for syncing

[Hugh Dickins]

On Tue, 12 Mar 2002, Chris Mason wrote:
> 
> But, the loop in sync_supers(dev == 0) is harder, it expects
> some flag it can check, and it expects the callback to the FS
> will clear that flag.  Adding a new flag seemed like more fun
> than redoing the locking and super walk.  I'm curious to hear what 
> Al thinks of it though.

Sorry if this is irrelevant to your case (wasn't following the thread),
but we noticed that repeatedly-restarting sync_supers() loop some while
back.  Would this patch help?

Hugh

--- 2.4.19-pre3/fs/super.c	Tue Mar 12 02:16:52 2002
+++ linux/fs/super.c	Wed Mar 13 20:27:54 2002
@@ -398,6 +398,7 @@
 	struct file_system_type *fs = s->s_type;
 
 	spin_lock(&sb_lock);
+	s->s_type = NULL;
 	list_del(&s->s_list);
 	list_del(&s->s_instances);
 	spin_unlock(&sb_lock);
@@ -461,19 +462,25 @@
 		}
 		return;
 	}
-restart:
 	spin_lock(&sb_lock);
+restart:
 	sb = sb_entry(super_blocks.next);
-	while (sb != sb_entry(&super_blocks))
+	while (sb != sb_entry(&super_blocks)) {
 		if (sb->s_dirt) {
 			sb->s_count++;
 			spin_unlock(&sb_lock);
 			down_read(&sb->s_umount);
 			write_super(sb);
-			drop_super(sb);
-			goto restart;
-		} else
-			sb = sb_entry(sb->s_list.next);
+			up_read(&sb->s_umount);
+			spin_lock(&sb_lock);
+			if (!--sb->s_count) {
+				destroy_super(sb);
+				goto restart;
+			} else if (!sb->s_type)
+				goto restart;
+		}
+		sb = sb_entry(sb->s_list.next);
+	}
 	spin_unlock(&sb_lock);
 }