From fb924b7b8669503582e003dd7b7340ee49029801 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Fri, 15 Aug 2025 15:23:08 -0400 Subject: [PATCH] change_mnt_propagation(): calculate propagation source only if we'll need it 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" Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- 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 { -- 2.25.1