[PATCH 09/12] doc: explain norandommap restriction and small remainder of zonemode=zbd

The recent commit "zbd: set norandommap=1 when zonemode=zbd is
specified" introduced norandommap=1 restriction for the zbd zonemode.
Also, the recent commit "zbd: write zone remainders smaller than minimum
block size" changed the handling of the small remainder at zone end.
Describe them in the documents.

Signed-off-by: Shin'ichiro Kawasaki <[email protected]>
---
 HOWTO.rst | 9 ++++++++-
 fio.1     | 7 ++++++-
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/HOWTO.rst b/HOWTO.rst
index b1642cf0..cd5edd01 100644
--- a/HOWTO.rst
+++ b/HOWTO.rst
@@ -1034,7 +1034,14 @@ Target file/device
 				all zones instead of being restricted to a
 				single zone. The :option:`zoneskip` parameter
 				is ignored. :option:`zonerange` and
-				:option:`zonesize` must be identical.
+				:option:`zonesize` must be identical. The option
+				:option:`norandommap` must be set to 1.
+				Otherwise it is automatically set. When the
+				block size is not aligned to the zone size,
+				write operations leave small areas at zone ends.
+				Fio truncates the specified block size to fill
+				the small left areas with write size smaller
+				than the block size.
 				Trim is handled using a zone reset operation.
 				Trim only considers non-empty sequential write
 				required and sequential write preferred zones.
diff --git a/fio.1 b/fio.1
index 3ee154ed..f7552eb5 100644
--- a/fio.1
+++ b/fio.1
@@ -809,7 +809,12 @@ starts. The \fBzonecapacity\fR parameter is ignored.
 .B zbd
 Zoned block device mode. I/O happens sequentially in each zone, even if random
 I/O has been selected. Random I/O happens across all zones instead of being
-restricted to a single zone.
+restricted to a single zone. The \fBzoneskip\fR parameter is ignored.
+\fBzonerange\fR and \fBzonesize\fR must be identical. The option
+\fBnorandommap\fR must be set to 1. Otherwise it is automatically set. When the
+block size is not aligned to the zone size, write operations leave small areas
+at zone ends. Fio truncates the specified block size to fill the small left
+areas with write size smaller than the block size.
 Trim is handled using a zone reset operation. Trim only considers non-empty
 sequential write required and sequential write preferred zones.
 .RE
-- 
2.49.0