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Subject[PATCH AUTOSEL 4.18 045/131] device-dax: avoid hang on error before devm_memremap_pages()
Date
From: Stefan Hajnoczi <stefanha@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 <stefanha@redhat.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
drivers/dax/pmem.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/dax/pmem.c b/drivers/dax/pmem.c
index fd49b24fd6af..99e2aace8078 100644
--- a/drivers/dax/pmem.c
+++ b/drivers/dax/pmem.c
@@ -105,15 +105,19 @@ static int dax_pmem_probe(struct device *dev)
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);
--
2.17.1
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