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-rw-r--r--fs/afs/file.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/fs/afs/file.c b/fs/afs/file.c
index 3d33b221d9ca..ef2cc8f565d2 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -417,13 +417,17 @@ static void afs_add_open_mmap(struct afs_vnode *vnode)
static void afs_drop_open_mmap(struct afs_vnode *vnode)
{
- if (!atomic_dec_and_test(&vnode->cb_nr_mmap))
+ if (atomic_add_unless(&vnode->cb_nr_mmap, -1, 1))
return;
down_write(&vnode->volume->open_mmaps_lock);
- if (atomic_read(&vnode->cb_nr_mmap) == 0)
+ read_seqlock_excl(&vnode->cb_lock);
+ // the only place where ->cb_nr_mmap may hit 0
+ // see __afs_break_callback() for the other side...
+ if (atomic_dec_and_test(&vnode->cb_nr_mmap))
list_del_init(&vnode->cb_mmap_link);
+ read_sequnlock_excl(&vnode->cb_lock);
up_write(&vnode->volume->open_mmaps_lock);
flush_work(&vnode->cb_work);