linux-kernel - Re: [PATCH] libnvdimm: fix btt vs clear poison locking

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Message-ID: <CAPcyv4gr2NPrCC3hr8g6aM-N=SQPkmbmpKWw0byvRj2iYgMVjQ@mail.gmail.com>
Date:   Tue, 11 Apr 2017 13:10:22 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Jeff Moyer <jmoyer@...hat.com>
Cc:     "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] libnvdimm: fix btt vs clear poison locking

On Tue, Apr 11, 2017 at 1:08 PM, Jeff Moyer <jmoyer@...hat.com> wrote:
> Dan Williams <dan.j.williams@...el.com> writes:
>
>> As a minimal fix, disable error clearing when the BTT is enabled. For
>> the final fix a larger rework of the poison list locking is needed.
>
>> @@ -243,7 +243,15 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
>>       }
>>
>>       if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align))) {
>> -             if (IS_ALIGNED(offset, 512) && IS_ALIGNED(size, 512)) {
>> +             /*
>> +              * FIXME: nsio_rw_bytes() may be called from atomic
>> +              * context in the BTT case and nvdimm_clear_poison()
>> +              * takes a sleeping lock. Until the locking can be
>> +              * reworked this capability depends on !BTT or BROKEN.
>> +              */
>> +             if ((!IS_ENABLED(CONFIG_BTT) || IS_ENABLED(CONFIG_BROKEN))
>> +                             && IS_ALIGNED(offset, 512)
>> +                             && IS_ALIGNED(size, 512)) {
>
> I don't like that you've disabled clear error just because the btt
> driver was enabled.  Can't you do something like this, instead?

Ooh, yes we can and that's much better.