* [PATCH] device-dax: avoid hang on error before devm_memremap_pages()
@ 2018-07-31 14:32 Stefan Hajnoczi
2018-08-01 0:26 ` Dave Jiang
0 siblings, 1 reply; 3+ messages in thread
From: Stefan Hajnoczi @ 2018-07-31 14:32 UTC (permalink / raw)
To: linux-nvdimm; +Cc: linux-kernel, Stefan Hajnoczi
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>
---
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,
&dax_pmem->ref);
--
2.17.1
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^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] device-dax: avoid hang on error before devm_memremap_pages()
2018-07-31 14:32 [PATCH] device-dax: avoid hang on error before devm_memremap_pages() Stefan Hajnoczi
@ 2018-08-01 0:26 ` Dave Jiang
2018-09-11 6:02 ` Dan Williams
0 siblings, 1 reply; 3+ messages in thread
From: Dave Jiang @ 2018-08-01 0:26 UTC (permalink / raw)
To: Stefan Hajnoczi, linux-nvdimm; +Cc: linux-kernel
On 7/31/2018 7:32 AM, Stefan Hajnoczi wrote:
> 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>
Applied
> ---
> 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,
> &dax_pmem->ref);
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^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] device-dax: avoid hang on error before devm_memremap_pages()
2018-08-01 0:26 ` Dave Jiang
@ 2018-09-11 6:02 ` Dan Williams
0 siblings, 0 replies; 3+ messages in thread
From: Dan Williams @ 2018-09-11 6:02 UTC (permalink / raw)
To: Dave Jiang; +Cc: Linux Kernel Mailing List, Stefan Hajnoczi, linux-nvdimm
On Tue, Jul 31, 2018 at 5:26 PM, Dave Jiang <dave.jiang@intel.com> wrote:
>
>
> On 7/31/2018 7:32 AM, Stefan Hajnoczi wrote:
>>
>> 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>
>
>
> Applied
>
A similar problem exists in other devm_memremap_pages() users. I had a
more comprehensive fix in-flight that I will rebase on top of this
change.
https://lore.kernel.org/patchwork/patch/961576/
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^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-07-31 14:32 [PATCH] device-dax: avoid hang on error before devm_memremap_pages() Stefan Hajnoczi
2018-08-01 0:26 ` Dave Jiang
2018-09-11 6:02 ` Dan Williams
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