[RFC v3 1/2] libnvdimm: Add flush callback for virtio pmem

[Pankaj Gupta]

This patch adds functionality to perform flush from guest to host
over VIRTIO. We are registering a callback based on 'nd_region' type.
As virtio_pmem driver requires this special flush interface, for rest
of the region types we are registering existing flush function.
Also report the error returned by virtio flush interface.

Signed-off-by: Pankaj Gupta <pagupta@xxxxxxxxxx>
---
 drivers/nvdimm/nd.h          |  1 +
 drivers/nvdimm/pmem.c        |  4 ++--
 drivers/nvdimm/region_devs.c | 24 ++++++++++++++++++------
 include/linux/libnvdimm.h    |  5 ++++-
 4 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/drivers/nvdimm/nd.h b/drivers/nvdimm/nd.h
index 32e0364..1b62f79 100644
--- a/drivers/nvdimm/nd.h
+++ b/drivers/nvdimm/nd.h
@@ -159,6 +159,7 @@ struct nd_region {
 	struct badblocks bb;
 	struct nd_interleave_set *nd_set;
 	struct nd_percpu_lane __percpu *lane;
+	int (*flush)(struct device *dev);
 	struct nd_mapping mapping[0];
 };
 
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 9d71492..29fd2cd 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -180,7 +180,7 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 	struct nd_region *nd_region = to_region(pmem);
 
 	if (bio->bi_opf & REQ_FLUSH)
-		nvdimm_flush(nd_region);
+		bio->bi_status = nvdimm_flush(nd_region);
 
 	do_acct = nd_iostat_start(bio, &start);
 	bio_for_each_segment(bvec, bio, iter) {
@@ -196,7 +196,7 @@ static blk_qc_t pmem_make_request(struct request_queue *q, struct bio *bio)
 		nd_iostat_end(bio, start);
 
 	if (bio->bi_opf & REQ_FUA)
-		nvdimm_flush(nd_region);
+		bio->bi_status = nvdimm_flush(nd_region);
 
 	bio_endio(bio);
 	return BLK_QC_T_NONE;
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index a612be6..124aae7 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1025,6 +1025,7 @@ static struct nd_region *nd_region_create(struct nvdimm_bus *nvdimm_bus,
 	dev->of_node = ndr_desc->of_node;
 	nd_region->ndr_size = resource_size(ndr_desc->res);
 	nd_region->ndr_start = ndr_desc->res->start;
+	nd_region->flush = ndr_desc->flush;
 	nd_device_register(dev);
 
 	return nd_region;
@@ -1065,13 +1066,10 @@ struct nd_region *nvdimm_volatile_region_create(struct nvdimm_bus *nvdimm_bus,
 }
 EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create);
 
-/**
- * nvdimm_flush - flush any posted write queues between the cpu and pmem media
- * @nd_region: blk or interleaved pmem region
- */
-void nvdimm_flush(struct nd_region *nd_region)
+void pmem_flush(struct device *dev)
 {
-	struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
+	struct nd_region_data *ndrd = dev_get_drvdata(dev);
+	struct nd_region *nd_region = to_nd_region(dev);
 	int i, idx;
 
 	/*
@@ -1094,6 +1092,20 @@ void nvdimm_flush(struct nd_region *nd_region)
 			writeq(1, ndrd_get_flush_wpq(ndrd, i, idx));
 	wmb();
 }
+
+/**
+ * nvdimm_flush - flush any posted write queues between the cpu and pmem media
+ * @nd_region: blk or interleaved pmem region
+ */
+int nvdimm_flush(struct nd_region *nd_region)
+{
+	if (nd_region->flush)
+		return(nd_region->flush(&nd_region->dev));
+
+	pmem_flush(&nd_region->dev);
+
+	return 0;
+}
 EXPORT_SYMBOL_GPL(nvdimm_flush);
 
 /**
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index 097072c..33b617f 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -126,6 +126,7 @@ struct nd_region_desc {
 	int numa_node;
 	unsigned long flags;
 	struct device_node *of_node;
+	int (*flush)(struct device *dev);
 };
 
 struct device;
@@ -201,7 +202,9 @@ unsigned long nd_blk_memremap_flags(struct nd_blk_region *ndbr);
 unsigned int nd_region_acquire_lane(struct nd_region *nd_region);
 void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane);
 u64 nd_fletcher64(void *addr, size_t len, bool le);
-void nvdimm_flush(struct nd_region *nd_region);
+int nvdimm_flush(struct nd_region *nd_region);
+void pmem_set_flush(struct nd_region *nd_region, void (*flush)
+					(struct device *));
 int nvdimm_has_flush(struct nd_region *nd_region);
 int nvdimm_has_cache(struct nd_region *nd_region);
 
-- 
2.9.3