From 62400dc79bdbde5fe2afcadf335d0ba58f44d240 Mon Sep 17 00:00:00 2001
From: John Spray <john.spray@redhat.com>
Date: Mon, 5 Nov 2018 10:56:04 +0000
Subject: [PATCH] osd: set lower bound+docs on osd_max_write_size

It never makes sense to set this below 4 megabytes (no
sane OSD backend would have a problem with writes of
that size), and doing so is a quick way to break your
cluster.

Also fill out doc fields.

Signed-off-by: John Spray <john.spray@redhat.com>
---
 src/common/options.cc | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/common/options.cc b/src/common/options.cc
index e07bf90d171..ee2ed9a319d 100644
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -2102,8 +2102,13 @@ std::vector<Option> get_global_options() {
     .set_description(""),
 
     Option("osd_max_write_size", Option::TYPE_SIZE, Option::LEVEL_ADVANCED)
+    .set_min(4)
     .set_default(90)
-    .set_description(""),
+    .set_description("Maximum size of a RADOS write operation in megabytes")
+    .set_long_description("This setting prevents clients from doing "
+        "very large writes to RADOS.  If you set this to a value "
+        "below what clients expect, they will receive an error "
+        "when attempting to write to the cluster."),
 
     Option("osd_max_pgls", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
     .set_default(1024)