doc: add lvol/blob deep copy descriptions

CHANGELOG.md, lvol.md and blob.md have been updated with
informations about the deep copy functionality.

Signed-off-by: Phan Le <phan.le@suse.com>

Author: PhanLe1010

CHANGELOG.md

@@ -388,6 +388,10 @@ These RPCs use the new API `spdk_lvol_shallow_copy()`.
 Added `bdev_lvol_set_parent` and `bdev_lvol_set_parent_bdev` RPC to change the parent of an existing lvol
 with the use of the new APIs `spdk_lvol_set_parent()` and `spdk_lvol_set_external_parent()`.
 
+Added `bdev_lvol_start_deep_copy` RPC to start a deep copy of an lvol over a given bdev and
+`bdev_lvol_check_deep_copy` RPC to get the status of the operation.
+These RPCs use the new API `spdk_lvol_deep_copy()`.
+
 ### nvme
 
 Added `spdk_nvme_ctrlr_get_max_sges()` API to retrieve maximum number of SGEs per request
@@ -480,6 +484,9 @@ like rebuild.
 Added `spdk_bs_grow_live()` and `spdk_bdev_update_bs_blockcnt()` API that can be used to
 increase size of blobstore filling the underlying device without first closing the blobstore.
 
+Added new API `spdk_bs_blob_deep_copy` to make a deep copy from a blob to a blobstore device. Only clusters
+allocated to the blob or blob's ancestors will be written on the device.
+
 ### env
 
 Added SPDK command line parameter `--no-huge`, which enables SPDK to run without hugepages.

doc/blob.md

@@ -446,6 +446,13 @@ than blob's size and blob store's block size must be an integer multiple of devi
 This functionality can be used to recreate the entire snapshot stack of a blob into a different blob
 store.
 
+#### Deep Copy {#blob_deep_copy}
+
+A read only blob can be copied over a blob store device in a way that only clusters
+allocated to the blob or blob's ancestors will be written on the device. This device must have a size equal or greater
+than blob's size and blob store's block size must be an integer multiple of device's block size.
+This functionality can be used to make a full copy of a blob into a different blob on the same or different blobstore.
+
 #### Change the parent of a blob {#blob_reparent}
 
 We can change the parent of a thin provisioned blob, making the blob a clone of a snapshot of the