doc: update krbd kernel recommendations

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/doc/start/os-recommendations.rst b/doc/start/os-recommendations.rst
index 4e9ff930e9b11d3a1ba992346e85c666579d4afd..58b9f520e3ebed3333a1bc53fda8aaf2ed195800 100644 (file)
--- a/doc/start/os-recommendations.rst
+++ b/doc/start/os-recommendations.rst
@@ -13,19 +13,22 @@ Linux Kernel
 
 - **Ceph Kernel Client**
 
-  We currently recommend:
+  If you are using the kernel client, the general advice is to *track* "stable"
+  or "longterm maintenance" kernel series provided by either http://kernel.org
+  or your distribution on the kernel client machines.
 
-  - 4.1.4 or later
-  - 3.16.3 or later (rbd deadlock regression in 3.16.[0-2])
-  - *NOT* 3.15.* (rbd deadlock regression)
-  - 3.14.*
+  For RBD, if you choose to *track* long-term kernels, we currently recommend
+  4.x-based "longterm maintenance" kernel series:
+
+  - 4.9.z
+  - 4.4.z
 
   These are considered pretty old, but if you must:
 
-  - 3.10.*
+  - 3.16.z
+  - 3.10.z
 
-  Firefly (CRUSH_TUNABLES3) tunables are supported starting with 3.15.
-  See `CRUSH Tunables`_ for more details.
+  Older kernel client versions may not support your `CRUSH tunables`_ profile.
 
 - **B-tree File System (Btrfs)**