diff --git a/man/systemd.resource-control.xml b/man/systemd.resource-control.xml
index ec3f6acbd5..fce7dc7505 100644
--- a/man/systemd.resource-control.xml
+++ b/man/systemd.resource-control.xml
@@ -462,6 +462,14 @@
This setting replaces BlockIODeviceWeight= and disables settings prefixed with
BlockIO or StartupBlockIO.
+
+ The specified device node should reference a block device that has an I/O scheduler
+ associated, i.e. should not refer to partition or loopback block devices, but to the originating,
+ physical device. When a path to a regular file or directory is specified it is attempted to
+ discover the correct originating device backing the file system of the specified path. This works
+ correctly only for simpler cases, where the file system is directly placed on a partition or
+ physical block device, or where simple 1:1 encryption using dm-crypt/LUKS is used. This discovery
+ does not cover complex storage and in particular RAID and volume management storage devices.
@@ -486,6 +494,8 @@
These settings replace BlockIOReadBandwidth= and
BlockIOWriteBandwidth= and disable settings prefixed with BlockIO or
StartupBlockIO.
+
+ Similar restrictions on block device discovery as for IODeviceWeight= apply, see above.
@@ -509,6 +519,8 @@
These settings are supported only if the unified control group hierarchy is used and disable settings
prefixed with BlockIO or StartupBlockIO.
+
+ Similar restrictions on block device discovery as for IODeviceWeight= apply, see above.
@@ -528,6 +540,8 @@
Implies IOAccounting=yes.
These settings are supported only if the unified control group hierarchy is used.
+
+ Similar restrictions on block device discovery as for IODeviceWeight= apply, see above.