Re: [PATCH] nvdimm, btt: make sure initializing new metadata clears poison

From: Dan Williams <dan.j.williams@intel.com>
To: Vishal Verma <vishal.l.verma@intel.com>
Cc: "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>
Subject: Re: [PATCH] nvdimm, btt: make sure initializing new metadata clears poison
Date: Mon, 8 May 2017 10:00:11 -0700	[thread overview]
Message-ID: <CAPcyv4hHRf6MEUxj1WvOjb9+JUmTBEh0x4RGGXEHg=kJT+anmg@mail.gmail.com> (raw)
In-Reply-To: <20170426224307.28075-1-vishal.l.verma@intel.com>

On Wed, Apr 26, 2017 at 3:43 PM, Vishal Verma <vishal.l.verma@intel.com> wrote:
> If we had badblocks/poison in the metadata area of a BTT, recreating the
> BTT would not clear the poison in all cases, notably the flog area. This
> is because rw_bytes will only clear errors if the request being sent
> down is 512B aligned and sized.
>
> Make sure that when writing the map and info blocks, the rw_bytes being
> sent are of the correct size/alignment. For the flog, instead of doing
> the smaller log_entry writes only, first do a 'wipe' of the entire area
> by writing zeroes in large enough chunks so that errors get cleared.

These eventually nsio_rw_bytes() while the namespace is claimed by a
btt instance, so this collides with the hack to disable error clearing
for btt. If we want to fix this up for 4.12 I think we need to pass a
'flags' parameter to the ->rw_bytes() routine to indicate that we are
in atomic context (NVDIMM_IO_ATOMIC), rather than assuming that all
BTT I/O is atomic. Care to code that up? I think we can include it in
a pull request before the merge window closes.
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