From: Stefan Bader <stefan.bader@canonical.com>
Date: Tue, 14 Jan 2014 15:26:50 +0100
Subject: Avoid meaningless error messages while probing for meta-data

This happens as device-mapper volumes are checked and kpartx creates
a 2 sector mapping if a device contains an extended partition.
Offsetting from the last sector backwards some probes overflow and
end up trying to seek to a very large offset (which fails and emits
a visible error message during device scanning).
This message is useless as such a small device would be pointless as
a RAID set anyway.
To fix this without larger changes, pragmatically ignore devices smaller
than 8 sectors (4K).

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

Index: dmraid-1.0.0.rc16/1.0.0.rc16/lib/format/format.c
===================================================================
--- dmraid-1.0.0.rc16.orig/1.0.0.rc16/lib/format/format.c	2014-01-14 15:50:17.554952405 +0100
+++ dmraid-1.0.0.rc16/1.0.0.rc16/lib/format/format.c	2014-01-14 15:50:35.319039242 +0100
@@ -533,6 +533,18 @@ read_raid_dev(struct lib_context *lc,
 	union read_info info;
 
 	/*
+	 * Kpartx will create a mapping for extended partitions which only
+	 * covers 2 sectors. That leads to error messages when looking for
+	 * meta-data as moving back from the last sector results in huge
+	 * offsets. Quick hack here to ignore any device smaller than 4K.
+	 */
+	if (di->sectors < 8) {
+		log_dbg(lc, "%s: Ignore device smaller than 4K (%s)",
+			handler, di->path);
+		return NULL;
+	}
+
+	/*
 	 * In case the metadata format handler provides a special
 	 * metadata read function, use that. If not, allocate and
 	 * read size from offset.