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From: Stefan Hajnoczi <stefanha@redhat.com>
To: linux-nvdimm@lists.01.org
Cc: linux-kernel@vger.kernel.org, Stefan Hajnoczi <stefanha@redhat.com>
Subject: [PATCH] device-dax: avoid hang on error before devm_memremap_pages()
Date: Tue, 31 Jul 2018 15:32:46 +0100	[thread overview]
Message-ID: <20180731143246.16915-1-stefanha@redhat.com> (raw)

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,
  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>
Found by code inspection.  Compile-tested only.
 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,

Linux-nvdimm mailing list

             reply	other threads:[~2018-07-31 14:32 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-31 14:32 Stefan Hajnoczi [this message]
2018-08-01  0:26 ` [PATCH] device-dax: avoid hang on error before devm_memremap_pages() Dave Jiang
2018-09-11  6:02   ` Dan Williams

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