On Mon, Jul 17, 2017 at 4:56 PM, Vishal Verma <vishal.l.verma@xxxxxxxxx> wrote:
> With the ACPI NFIT 'DSM' methods, acpi can be called from IO paths.
> Specifically, the DSM to clear media errors is called during writes, so
> that we can provide a writes-fix-errors model.
>
> However it is easy to imagine a scenario like:
> -> write through the nvdimm driver
> -> acpi allocation
> -> writeback, causes more IO through the nvdimm driver
> -> deadlock
>
> Fix this by using memalloc_noio_{save,restore}, which sets the GFP_NOIO
> flag for the current scope when issuing commands/IOs that are expected
> to clear errors.
>
> Cc: <linux-acpi@xxxxxxxxxxxxxxx>
> Cc: <linux-nvdimm@xxxxxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Robert Moore <robert.moore@xxxxxxxxx>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Looks good to me. Please move this up in the series before we start
calling nvdimm_clear_poison() in the btt I/O path so there's no
bisection point where this deadlock comes back.
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