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Date:   Fri, 26 Jul 2019 00:31:12 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Stephen Rothwell <sfr@canb.auug.org.au>
Cc:     Linux Next Mailing List <linux-next@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Nikolay Borisov <nborisov@suse.com>
Subject: Re: linux-next: run time BUG after merge of the vfs-fixes tree?
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References: <20190725144712.39cb1e5b@canb.auug.org.au>
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On Thu, Jul 25, 2019 at 02:47:12PM +1000, Stephen Rothwell wrote:
> Hi all,
> 
> During my qemu boot tests (powerpc64 pseries_le_defconfig) today, I got
> the following BUG:

... caused by mismerge.  #fixes does
@@ -1471,10 +1470,11 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
                                list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
                        } else {
                                umount_mnt(p);
-                               hlist_add_head(&p->mnt_umount, &unmounted);
                        }
                }
                change_mnt_propagation(p, MS_PRIVATE);
+               if (disconnect)
+                       hlist_add_head(&p->mnt_umount, &unmounted);
        }
 }
and your merge has dropped the removal part - it has
                                list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
                        } else {
                                umount_mnt(p);
                                hlist_add_head(&p->mnt_umount, &unmounted);
                        }
                }
                change_mnt_propagation(p, MS_PRIVATE);
                if (disconnect)
                        hlist_add_head(&p->mnt_umount, &unmounted);
        }
}

Should've #work.dcache from there once (equal) #work.dcache2 got pulled ;-/