nvmet: Optionally use PCI P2P memory

Create a configfs attribute in each nvme-fabrics namespace to enable P2P
memory use.  The attribute may be enabled (with a boolean) or a specific
P2P device may be given (with the device's PCI name).

When enabled, the namespace will ensure the underlying block device
supports P2P and is compatible with any specified P2P device.  If no device
was specified it will ensure there is compatible P2P memory somewhere in
the system.  Enabling a namespace with P2P memory will fail with EINVAL
(and an appropriate dmesg error) if any of these conditions are not met.

Once a controller is set up on a specific port, the P2P device to use for
each namespace will be found and stored in a radix tree by namespace ID.
When memory is allocated for a request, the tree is used to look up the P2P
device to allocate memory against.  If no device is in the tree (because no
appropriate device was found), or if allocation of P2P memory fails, fall
back to using regular memory.

Signed-off-by: Stephen Bates <sbates@raithlin.com>
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
[hch: partial rewrite of the initial code]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index e7b7406c4e22..d6be098f342b 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -26,6 +26,7 @@
 #include <linux/configfs.h>
 #include <linux/rcupdate.h>
 #include <linux/blkdev.h>
+#include <linux/radix-tree.h>
 
 #define NVMET_ASYNC_EVENTS		4
 #define NVMET_ERROR_LOG_SLOTS		128
@@ -77,6 +78,9 @@ struct nvmet_ns {
 	struct completion	disable_done;
 	mempool_t		*bvec_pool;
 	struct kmem_cache	*bvec_cache;
+
+	int			use_p2pmem;
+	struct pci_dev		*p2p_dev;
 };
 
 static inline struct nvmet_ns *to_nvmet_ns(struct config_item *item)
@@ -84,6 +88,11 @@ static inline struct nvmet_ns *to_nvmet_ns(struct config_item *item)
 	return container_of(to_config_group(item), struct nvmet_ns, group);
 }
 
+static inline struct device *nvmet_ns_dev(struct nvmet_ns *ns)
+{
+	return ns->bdev ? disk_to_dev(ns->bdev->bd_disk) : NULL;
+}
+
 struct nvmet_cq {
 	u16			qid;
 	u16			size;
@@ -184,6 +193,9 @@ struct nvmet_ctrl {
 
 	char			subsysnqn[NVMF_NQN_FIELD_LEN];
 	char			hostnqn[NVMF_NQN_FIELD_LEN];
+
+	struct device *p2p_client;
+	struct radix_tree_root p2p_ns_map;
 };
 
 struct nvmet_subsys {
@@ -294,6 +306,9 @@ struct nvmet_req {
 
 	void (*execute)(struct nvmet_req *req);
 	const struct nvmet_fabrics_ops *ops;
+
+	struct pci_dev *p2p_dev;
+	struct device *p2p_client;
 };
 
 extern struct workqueue_struct *buffered_io_wq;