NVMe: Configure support for block flush

This configures an nvme request_queue as flush capable if the device
has a volatile write cache present.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

drivers/block/nvme-core.c

@@ -1897,6 +1897,8 @@ static struct nvme_ns *nvme_alloc_ns(struct nvme_dev *dev, unsigned nsid,
 	blk_queue_logical_block_size(ns->queue, 1 << ns->lba_shift);
 	if (dev->max_hw_sectors)
 		blk_queue_max_hw_sectors(ns->queue, dev->max_hw_sectors);
+	if (dev->vwc & NVME_CTRL_VWC_PRESENT)
+		blk_queue_flush(ns->queue, REQ_FLUSH | REQ_FUA);
 
 	disk->major = nvme_major;
 	disk->first_minor = 0;
@@ -2201,6 +2203,7 @@ static int nvme_dev_add(struct nvme_dev *dev)
 	nn = le32_to_cpup(&ctrl->nn);
 	dev->oncs = le16_to_cpup(&ctrl->oncs);
 	dev->abort_limit = ctrl->acl + 1;
+	dev->vwc = ctrl->vwc;
 	memcpy(dev->serial, ctrl->sn, sizeof(ctrl->sn));
 	memcpy(dev->model, ctrl->mn, sizeof(ctrl->mn));
 	memcpy(dev->firmware_rev, ctrl->fr, sizeof(ctrl->fr));

include/linux/nvme.h

@@ -99,6 +99,7 @@ struct nvme_dev {
 	u32 stripe_size;
 	u16 oncs;
 	u16 abort_limit;
+	u8 vwc;
 	u8 initialized;
 };
 

include/uapi/linux/nvme.h

@@ -73,6 +73,7 @@ enum {
 	NVME_CTRL_ONCS_COMPARE			= 1 << 0,
 	NVME_CTRL_ONCS_WRITE_UNCORRECTABLE	= 1 << 1,
 	NVME_CTRL_ONCS_DSM			= 1 << 2,
+	NVME_CTRL_VWC_PRESENT			= 1 << 0,
 };
 
 struct nvme_lbaf {