I forgot to commit part of the patch.  Attached is the patch in full.

David
---
commit a3d01f1a21bcf2c39aa6db49edbc08540378a593
Author: David Howells <dhowe...@redhat.com>
Date:   Mon Dec 13 16:26:44 2021 +0000

    afs: Fix mmap
    
    Fix afs_add_open_map() to check that the vnode isn't already on the list
    when it adds it.  It's possible that afs_drop_open_mmap() decremented the
    cb_nr_mmap counter, but hadn't yet got into the locked section to remove
    it.
    
    Also vnode->cb_mmap_link should be initialised, so fix that too.
    
    Fixes: 6e0e99d58a65 ("afs: Fix mmap coherency vs 3rd-party changes")
    Reported-by: Marc Dionne <marc.dio...@auristor.com>
    Signed-off-by: David Howells <dhowe...@redhat.com>
    cc: linux-...@lists.infradead.org

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 572063dad0b3..bcda99dcfdec 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -539,8 +539,9 @@ static void afs_add_open_mmap(struct afs_vnode *vnode)
        if (atomic_inc_return(&vnode->cb_nr_mmap) == 1) {
                down_write(&vnode->volume->cell->fs_open_mmaps_lock);
 
-               list_add_tail(&vnode->cb_mmap_link,
-                             &vnode->volume->cell->fs_open_mmaps);
+               if (list_empty(&vnode->cb_mmap_link))
+                       list_add_tail(&vnode->cb_mmap_link,
+                                     &vnode->volume->cell->fs_open_mmaps);
 
                up_write(&vnode->volume->cell->fs_open_mmaps_lock);
        }
diff --git a/fs/afs/super.c b/fs/afs/super.c
index af7cbd9949c5..5ec9fd97eccc 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -668,6 +668,7 @@ static void afs_i_init_once(void *_vnode)
        INIT_LIST_HEAD(&vnode->pending_locks);
        INIT_LIST_HEAD(&vnode->granted_locks);
        INIT_DELAYED_WORK(&vnode->lock_work, afs_lock_work);
+       INIT_LIST_HEAD(&vnode->cb_mmap_link);
        seqlock_init(&vnode->cb_lock);
 }
 

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