doc: suppored features of kernel client

Fixes: http://tracker.ceph.com/issues/27209
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>

doc/cephfs/index.rst

@@ -75,6 +75,7 @@ authentication keyring.
 	Mount CephFS as FUSE <fuse>
 	Mount CephFS in fstab <fstab>
 	Use the CephFS Shell <cephfs-shell>
+	Supported Features of Kernel Driver <kernel-features>
 	Manpage ceph-fuse <../../man/8/ceph-fuse>
 	Manpage mount.ceph <../../man/8/mount.ceph>
 	Manpage mount.fuse.ceph <../../man/8/mount.fuse.ceph>

doc/cephfs/kernel-features.rst

@@ -0,0 +1,40 @@
+
+Supported Features of Kernel Driver
+========================================
+
+Inline data
+-----------
+Inline data was introduced by the Firefly release. Linux kernel clients >= 3.19
+can read inline data, can convert existing inline data to RADOS objects when
+file data is modified. At present, Linux kernel clients do not store file data
+as inline data.
+
+See `Experimental Features`_ for more information.
+
+Quotas
+------
+Quota was first introduced by the hammer release. Quota disk format got renewed
+by the Mimic release. Linux kernel clients >= 4.17 can support the new format
+quota. At present, no Linux kernel client support the old format quota.
+
+See `Quotas`_ for more information.
+
+Multiple filesystems within a Ceph cluster
+------------------------------------------
+The feature was introduced by the Jewel release. Linux kernel clients >= 4.7
+can support it.
+
+See `Experimental Features`_ for more information.
+
+Multiple active metadata servers
+--------------------------------
+The feature has been supported since the Luminous release. It is recommended to
+use Linux kernel clients >= 4.14 when there are multiple active MDS.
+
+Snapshots
+---------
+The feature has been supported since the Mimic release. It is recommended to
+use Linux kernel clients >= 4.17 if snapshot is used.
+
+.. _Experimental Features: ../experimental-features
+.. _Quotas: ../quota