[PATCH 4.18 085/158] device-dax: avoid hang on error before devm_memremap_pages()

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Hajnoczi <stefa...@redhat.com>

[ Upstream commit b7751410c180a05fdc21268f8661b1480169b0df ]

dax_pmem_percpu_exit() waits for dax_pmem_percpu_release() to invoke the
dax_pmem->cmp completion.  Unfortunately this approach to cleaning up
the percpu_ref only works after devm_memremap_pages() was successful.

If devm_add_action_or_reset() or devm_memremap_pages() fails,
dax_pmem_percpu_release() is not invoked.  Therefore
dax_pmem_percpu_exit() hangs waiting for the completion:

  rc = devm_add_action_or_reset(dev, dax_pmem_percpu_exit,
                                &dax_pmem->ref);
  if (rc)
        return rc;

  dax_pmem->pgmap.ref = &dax_pmem->ref;
  addr = devm_memremap_pages(dev, &dax_pmem->pgmap);

Avoid the hang by calling percpu_ref_exit() in the error paths instead
of going through dax_pmem_percpu_exit().

Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
Signed-off-by: Dave Jiang <dave.ji...@intel.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/dax/pmem.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -105,15 +105,19 @@ static int dax_pmem_probe(struct device
        if (rc)
                return rc;
 
-       rc = devm_add_action_or_reset(dev, dax_pmem_percpu_exit,
-                                                       &dax_pmem->ref);
-       if (rc)
+       rc = devm_add_action(dev, dax_pmem_percpu_exit, &dax_pmem->ref);
+       if (rc) {
+               percpu_ref_exit(&dax_pmem->ref);
                return rc;
+       }
 
        dax_pmem->pgmap.ref = &dax_pmem->ref;
        addr = devm_memremap_pages(dev, &dax_pmem->pgmap);
-       if (IS_ERR(addr))
+       if (IS_ERR(addr)) {
+               devm_remove_action(dev, dax_pmem_percpu_exit, &dax_pmem->ref);
+               percpu_ref_exit(&dax_pmem->ref);
                return PTR_ERR(addr);
+       }
 
        rc = devm_add_action_or_reset(dev, dax_pmem_percpu_kill,
                                                        &dax_pmem->ref);