linux-kernel - Re: [PATCH 3/6] libnvdimm/region: Register badblocks before namespaces

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Date:   Fri, 21 Jun 2019 00:56:24 +0000
From:   "Verma, Vishal L" <vishal.l.verma@...el.com>
To:     "Williams, Dan J" <dan.j.williams@...el.com>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH 3/6] libnvdimm/region: Register badblocks before
 namespaces

On Tue, 2019-06-11 at 16:25 -0700, Dan Williams wrote:
> Namespace activation expects to be able to reference region badblocks.
> The following warning sometimes triggers when asynchronous namespace
> activation races in front of the completion of namespace probing. Move
> all possible namespace probing after region badblocks initialization.
> 
> Otherwise, lockdep sometimes catches the uninitialized state of the
> badblocks seqlock with stack trace signatures like:
> 
>     INFO: trying to register non-static key.
>     pmem2: detected capacity change from 0 to 136365211648
>     the code is fine but needs lockdep annotation.
>     turning off the locking correctness validator.
>     CPU: 9 PID: 358 Comm: kworker/u80:5 Tainted:
> G           OE     5.2.0-rc4+ #3382
>     Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0
> 02/06/2015
>     Workqueue: events_unbound async_run_entry_fn
>     Call Trace:
>      dump_stack+0x85/0xc0
>     pmem1.12: detected capacity change from 0 to 8589934592
>      register_lock_class+0x56a/0x570
>      ? check_object+0x140/0x270
>      __lock_acquire+0x80/0x1710
>      ? __mutex_lock+0x39d/0x910
>      lock_acquire+0x9e/0x180
>      ? nd_pfn_validate+0x28f/0x440 [libnvdimm]
>      badblocks_check+0x93/0x1f0
>      ? nd_pfn_validate+0x28f/0x440 [libnvdimm]
>      nd_pfn_validate+0x28f/0x440 [libnvdimm]
>      ? lockdep_hardirqs_on+0xf0/0x180
>      nd_dax_probe+0x9a/0x120 [libnvdimm]
>      nd_pmem_probe+0x6d/0x180 [nd_pmem]
>      nvdimm_bus_probe+0x90/0x2c0 [libnvdimm]
> 
> Fixes: 48af2f7e52f4 ("libnvdimm, pfn: during init, clear errors...")
> Cc: <stable@...r.kernel.org>
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  drivers/nvdimm/region.c |   22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)

This looks good to me,
Reviewed-by: Vishal Verma <vishal.l.verma@...el.com>

> 
> diff --git a/drivers/nvdimm/region.c b/drivers/nvdimm/region.c
> index ef46cc3a71ae..488c47ac4c4a 100644
> --- a/drivers/nvdimm/region.c
> +++ b/drivers/nvdimm/region.c
> @@ -34,17 +34,6 @@ static int nd_region_probe(struct device *dev)
>  	if (rc)
>  		return rc;
>  
> -	rc = nd_region_register_namespaces(nd_region, &err);
> -	if (rc < 0)
> -		return rc;
> -
> -	ndrd = dev_get_drvdata(dev);
> -	ndrd->ns_active = rc;
> -	ndrd->ns_count = rc + err;
> -
> -	if (rc && err && rc == err)
> -		return -ENODEV;
> -
>  	if (is_nd_pmem(&nd_region->dev)) {
>  		struct resource ndr_res;
>  
> @@ -60,6 +49,17 @@ static int nd_region_probe(struct device *dev)
>  		nvdimm_badblocks_populate(nd_region, &nd_region->bb,
> &ndr_res);
>  	}
>  
> +	rc = nd_region_register_namespaces(nd_region, &err);
> +	if (rc < 0)
> +		return rc;
> +
> +	ndrd = dev_get_drvdata(dev);
> +	ndrd->ns_active = rc;
> +	ndrd->ns_count = rc + err;
> +
> +	if (rc && err && rc == err)
> +		return -ENODEV;
> +
>  	nd_region->btt_seed = nd_btt_create(nd_region);
>  	nd_region->pfn_seed = nd_pfn_create(nd_region);
>  	nd_region->dax_seed = nd_dax_create(nd_region);
>