Revert "nvme-pci: Disable Host Memory Buffer usage"

This reverts commit 4263812.

Author: altserg

drivers/nvme/host/pci.c

@@ -2081,7 +2081,6 @@ static void nvme_free_host_mem(struct nvme_dev *dev)
 	dev->nr_host_mem_descs = 0;
 }
 
-#if 0
 static int __nvme_alloc_host_mem(struct nvme_dev *dev, u64 preferred,
 		u32 chunk_size)
 {
@@ -2150,11 +2149,9 @@ static int __nvme_alloc_host_mem(struct nvme_dev *dev, u64 preferred,
 	dev->host_mem_descs = NULL;
 	return -ENOMEM;
 }
-#endif
 
 static int nvme_alloc_host_mem(struct nvme_dev *dev, u64 min, u64 preferred)
 {
-#if 0
 	u64 min_chunk = min_t(u64, preferred, PAGE_SIZE * MAX_ORDER_NR_PAGES);
 	u64 hmminds = max_t(u32, dev->ctrl.hmminds * 4096, PAGE_SIZE * 2);
 	u64 chunk_size;
@@ -2167,7 +2164,6 @@ static int nvme_alloc_host_mem(struct nvme_dev *dev, u64 min, u64 preferred)
 			nvme_free_host_mem(dev);
 		}
 	}
-#endif
 
 	return -ENOMEM;
 }