Incremental: improve support for "DEVICE" based restriction in mdadm.conf

--incremental currently fails if the device name passed does not
textually match the names permitted by the DEVICE line in mdadm.conf.
This is problematic when "mdadm -I" is run by udev as the name given
can be a temp name.

This patch makes two improvements:
1/ We generate a list of all existing devices that match the names
  in mdadm.conf, and allow rdev based matching
2/ We allows extra aliases to be provided on the command line, and
  perform textual matching on those.  This is particularly suitable
  for udev usages as ${DEVLINKS} can be provided even though the links
  make not yet be created.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 10 insertions, 2 deletions

diff --git a/mdadm.8.in b/mdadm.8.in
index f49822ec..edbedc40 100644
--- a/mdadm.8.in
+++ b/mdadm.8.in
@@ -2676,6 +2676,7 @@ Usage:
 .RB [ \-\-run ]
 .RB [ \-\-quiet ]
 .I component-device
+.RI [ optional-aliases-for-device ]
 .HP 12
 Usage:
 .B mdadm \-\-incremental \-\-fail
@@ -2730,16 +2731,23 @@ That is, is it listed in a
 .B DEVICES
 line in that file.  If
 .B DEVICES
-is absent then the default it to allow any device.  Similar if
+is absent then the default it to allow any device.  Similarly if
 .B DEVICES
 contains the special word
 .B partitions
 then any device is allowed.  Otherwise the device name given to
-.I mdadm
+.IR mdadm ,
+or one of the aliases given, or an alias found in the filesystem,
 must match one of the names or patterns in a
 .B DEVICES
 line.
 
+This is the only context where the aliases are used.  They are
+usually provided by a
+.I udev
+rules mentioning
+.BR ${DEVLINKS} .
+
 .IP +
 Does the device have a valid md superblock?  If a specific metadata
 version is requested with