propagate_one(): separate the "what should be the master for this copy" part

When we create the first copy for a peer group, it becomes a slave of
one of the existing copies; take that logics into a separate helper -
find_master(parent, last_copy, original).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/pnode.c b/fs/pnode.c
index 7c832f98595cf833cc84b149441f4ae797af86a8..94de8aad4da567b11e7f4a3a7e11d8b028c8f0cf 100644 (file)
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -232,6 +232,31 @@ static bool need_secondary(struct mount *m, struct mountpoint *dest_mp)
        return true;
 }
 
+static struct mount *find_master(struct mount *m,
+                               struct mount *last_copy,
+                               struct mount *original)
+{
+       struct mount *p;
+
+       // ascend until there's a copy for something with the same master
+       for (;;) {
+               p = m->mnt_master;
+               if (!p || IS_MNT_MARKED(p))
+                       break;
+               m = p;
+       }
+       while (!peers(last_copy, original)) {
+               struct mount *parent = last_copy->mnt_parent;
+               if (parent->mnt_master == p) {
+                       if (!peers(parent, m))
+                               last_copy = last_copy->mnt_master;
+                       break;
+               }
+               last_copy = last_copy->mnt_master;
+       }
+       return last_copy;
+}
+
 static int propagate_one(struct mount *m, struct mountpoint *dest_mp)
 {
        struct mount *child;
@@ -240,23 +265,7 @@ static int propagate_one(struct mount *m, struct mountpoint *dest_mp)
        if (peers(m, last_dest)) {
                type = CL_MAKE_SHARED;
        } else {
-               struct mount *n, *p;
-               bool done;
-               for (n = m; ; n = p) {
-                       p = n->mnt_master;
-                       if (!p || IS_MNT_MARKED(p))
-                               break;
-               }
-               do {
-                       struct mount *parent = last_source->mnt_parent;
-                       if (peers(last_source, first_source))
-                               break;
-                       done = parent->mnt_master == p;
-                       if (done && peers(n, parent))
-                               break;
-                       last_source = last_source->mnt_master;
-               } while (!done);
-
+               last_source = find_master(m, last_source, first_source);
                type = CL_SLAVE;
                /* beginning of peer group among the slaves? */
                if (IS_MNT_SHARED(m))