On Mon, Apr 24, 2017 at 10:03 AM, Linda Knippers <linda.knippers@xxxxxxx> wrote: > 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? For an application that wants to shutdown and sync. Basically I wanted to make it clear that with this interface the buffers can be synced regardless of any downstream namespace configuration or state. > >> 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? No, I'm making the change that Masayoshi-san suggested to move the flush to a write operation... assuming we move forward given Jeff's concern. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
