We only need it when mount in question was sending events downstream (then
recepients need to switch to new master) or the mount is being turned into
slave (then we need a new master for it).
That wouldn't be a big deal, except that it causes quite a bit of work
when umount_tree() is taking a large peer group out. Adding a trivial
"don't bother calling propagation_source() unless we are going to use
its results" logics improves the things quite a bit.
We are still doing unnecessary work on bulk removals from propagation graph,
but the full solution for that will have to wait for the next merge window.
Fixes: 955336e204ab "do_make_slave(): choose new master sanely"
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/pnode.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/pnode.c b/fs/pnode.c
index 1c789f88b3d2..6f7d02f3fa98 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -111,7 +111,8 @@ void change_mnt_propagation(struct mount *mnt, int type)
return;
}
if (IS_MNT_SHARED(mnt)) {
- m = propagation_source(mnt);
+ if (type == MS_SLAVE || !hlist_empty(&mnt->mnt_slave_list))
+ m = propagation_source(mnt);
if (list_empty(&mnt->mnt_share)) {
mnt_release_group_id(mnt);
} else {
--
2.47.2
