Currently, attempts to shutdown and re-enable a device-dax instance trigger: Missing reference count teardown definition WARNING: CPU: 37 PID: 1608 at mm/memremap.c:211 devm_memremap_pages+0x234/0x850 [..] RIP: 0010:devm_memremap_pages+0x234/0x850 [..] Call Trace: dev_dax_probe+0x66/0x190 [device_dax] really_probe+0xef/0x390 driver_probe_device+0xb4/0x100 device_driver_attach+0x4f/0x60 Given that the setup path initializes pgmap->ref, arrange for it to be also torn down so devm_memremap_pages() is ready to be called again and not be mistaken for the 3rd-party per-cpu-ref case. Fixes: 24917f6b1041 ("memremap: provide an optional internal refcount in struct dev_pagemap") Reported-by: Fan Du <fan.du@xxxxxxxxx> Tested-by: Vishal Verma <vishal.l.verma@xxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Ira Weiny <ira.weiny@xxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> --- Andrew, I have another dax fix pending, so I'm ok to take this through the nvdimm tree, holler if you want it in -mm. mm/memremap.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/mm/memremap.c b/mm/memremap.c index 6ee03a816d67..86432650f829 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -91,6 +91,12 @@ static void dev_pagemap_cleanup(struct dev_pagemap *pgmap) wait_for_completion(&pgmap->done); percpu_ref_exit(pgmap->ref); } + /* + * Undo the pgmap ref assignment for the internal case as the + * caller may re-enable the same pgmap. + */ + if (pgmap->ref == &pgmap->internal_ref) + pgmap->ref = NULL; } static void devm_memremap_pages_release(void *data)