On 04/21/2017 07:48 PM, Dan Williams wrote:
> The nvdimm_flush() mechanism helps to reduce the impact of an ADR
> (asynchronous-dimm-refresh) failure. The ADR mechanism handles flushing
> platform WPQ (write-pending-queue) buffers when power is removed. The
> nvdimm_flush() mechanism performs that same function on-demand.
>
> When a pmem namespace is associated with a block device, an
> nvdimm_flush() is triggered with every block-layer REQ_FUA, or REQ_FLUSH
> request. However, when a namespace is in device-dax mode, or namespaces
> are disabled, userspace needs another path.
Why would a user need to flush a disabled namespace?
> The new 'flush' attribute is visible when it can be determined that the
> interleave-set either does, or does not have DIMMs that expose WPQ-flush
> addresses, "flush-hints" in ACPI NFIT terminology. It returns "1" and
> flushes DIMMs, or returns "0" the flush operation is a platform nop.
It seems a little odd to me that reading a read-only attribute both
tells you that the device has flush hints and also triggers a flush.
This means that anyone at any time can cause a flush. Do we want that?
-- ljk
>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
> drivers/nvdimm/region_devs.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index 8de5a04644a1..3495b4c23941 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -255,6 +255,19 @@ static ssize_t size_show(struct device *dev,
> }
> static DEVICE_ATTR_RO(size);
>
> +static ssize_t flush_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct nd_region *nd_region = to_nd_region(dev);
> +
> + if (nvdimm_has_flush(nd_region)) {
> + nvdimm_flush(nd_region);
> + return sprintf(buf, "1\n");
> + }
> + return sprintf(buf, "0\n");
> +}
> +static DEVICE_ATTR_RO(flush);
> +
> static ssize_t mappings_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> @@ -474,6 +487,7 @@ static DEVICE_ATTR_RO(resource);
>
> static struct attribute *nd_region_attributes[] = {
> &dev_attr_size.attr,
> + &dev_attr_flush.attr,
> &dev_attr_nstype.attr,
> &dev_attr_mappings.attr,
> &dev_attr_btt_seed.attr,
> @@ -508,6 +522,9 @@ static umode_t region_visible(struct kobject *kobj, struct attribute *a, int n)
> if (!is_nd_pmem(dev) && a == &dev_attr_resource.attr)
> return 0;
>
> + if (a == &dev_attr_flush.attr && nvdimm_has_flush(nd_region) < 0)
> + return 0;
> +
> if (a != &dev_attr_set_cookie.attr
> && a != &dev_attr_available_size.attr)
> return a->mode;
>
> _______________________________________________
> Linux-nvdimm mailing list
> Linux-nvdimm@xxxxxxxxxxxx
> https://lists.01.org/mailman/listinfo/linux-nvdimm
>
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