lvol: Documentation

Signed-off-by: Piotr Pelplinski <piotr.pelplinski@intel.com>
Change-Id: I23e14bd1568dade96e5503598a3e360c951d6d78
Reviewed-on: https://review.gerrithub.io/369250
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>

doc/Doxyfile

@@ -793,6 +793,7 @@ INPUT                  = ../include/spdk \
                          event.md \
                          ioat.md \
                          iscsi.md \
+                         lvol.md \
                          nvme.md \
                          nvme-cli.md \
                          nvmf.md \

doc/bdev.md

@@ -155,3 +155,8 @@ kill $nbd_pid
 # the first partition will be automatically exposed as
 # Nvme0n1p1 in SPDK applications.
 ~~~
+
+## Logical Volumes
+
+The SPDK lvol driver allows to dynamically partition other SPDK backends.
+No static configuration for this driver. Refer to @ref lvol for detailed RPC configuration.

doc/lvol.md

@@ -0,0 +1,28 @@
+# Logical volume store {#lvolstore}
+
+A logical volume store is an SPDK blobstore with a special super blob denoting the blobstore.
+This super blob is to different from SPDK blobstores used for BlobFS.
+
+# Logical volume {#lvol}
+
+A logical volume is an SPDK blob created from an lvolstore.
+
+An lvol is uniquely identified by its blob ID and the UUID of the lvolstore from which it was created.
+
+# Logical volume block device {#vdev_lvol}
+
+Representation of an SPDK block device (spdk_bdev) with an lvol implementation. A logical volume block device translates generic SPDK block device I/O (spdk_bdev_io) operations into the equivalent SPDK blob operations.
+
+# RPC overview
+There are few logical volumes specific calls.
+
+- construct_lvol_store bdev_name
+	Constructs lvolstore on specified bdev
+- destroy_lvol_store bdev_name
+	Destroy lvolstore on specified bdev
+- construct_lvol_bdev uuid size
+	Constructs lvol bdev on lvolstore specified by uuid with specified size
+- resize_lvol_bdev bdev_name size
+	Resizes specified lvol bdev
+
+Note that destroying lvol store requires using call destroy_lvol_store, while deleting single lvol requires using delete_bdev rpc call.