Re: [PATCH v5 1/6] libnvdimm: nd_region flush callback support

This patch adds functionality to perform flush from guest to host over VIRTIO. We are registering a callback based on 'nd_region' type. virtio_pmem driver requires this special flush function. For rest of the region types we are registering existing flush function. Report error returned by host fsync failure to userspace. This also handles asynchronous flush requests from the block layer by creating a child bio and chaining it with parent bio. Signed-off-by: Pankaj Gupta <pagupta(a)redhat.com&gt; ---

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c index b4ef7d9ff22e..fb1041ab32a6 100644 --- a/drivers/nvdimm/region_devs.c +++ b/drivers/nvdimm/region_devs.c @@ -295,7 +295,9 @@ static ssize_t deep_flush_store(struct device *dev, struct device_attribute *att return rc; if (!flush) return -EINVAL; - nvdimm_flush(nd_region); + rc = nvdimm_flush(nd_region, NULL, false); + if (rc) + return rc; return len; } @@ -1085,6 +1087,11 @@ 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; + if (ndr_desc->flush) + nd_region->flush = ndr_desc->flush; + else + nd_region->flush = generic_nvdimm_flush; + nd_device_register(dev); return nd_region; @@ -1125,11 +1132,36 @@ struct nd_region *nvdimm_volatile_region_create(struct nvdimm_bus *nvdimm_bus, } EXPORT_SYMBOL_GPL(nvdimm_volatile_region_create); +int nvdimm_flush(struct nd_region *nd_region, struct bio *bio, bool async) +{

+ int rc = 0; + + /* Create child bio for asynchronous flush and chain with + * parent bio. Otherwise directly call nd_region flush. + */ + if (async && bio->bi_iter.bi_sector != -1) { + + struct bio *child = bio_alloc(GFP_ATOMIC, 0); + + if (!child) + return -ENOMEM; + bio_copy_dev(child, bio); + child->bi_opf = REQ_PREFLUSH; + child->bi_iter.bi_sector = -1; + bio_chain(child, bio); + submit_bio(child);

+ } else { + if (nd_region->flush(nd_region)) + rc = -EIO;