From 06282373ff57a2b82621be4f84f981e1b0a4eb28 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 8 Aug 2019 14:43:49 -0700 Subject: [PATCH] mm/memremap: Fix reuse of pgmap instances with internal references 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 Tested-by: Vishal Verma Cc: Andrew Morton Cc: Christoph Hellwig Cc: Ira Weiny Cc: Jason Gunthorpe Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/156530042781.2068700.8733813683117819799.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams --- 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)