When a LUN is expanded, unable to resize ASM disks online

When a LUN is expanded, unable to resize ASM disk online.  However, able to resize the ASM disk after dismounting/remounting the ASM diskgroup  or restarting the ASM instance. No warnings are noticed in the Operating System while increasing the LUN.  The below error message is noticed in the ASM alert log file.

alert_ASM.log
===============

Wed Mar 18 12:24:36 2015
SQL> alter diskgroup  VRVLT_DBS resize disk VRVLT_DBS_0000 size 20g rebalance power 9  
NOTE: requesting all-instance membership refresh for group=2
ERROR: ORA-15057 signalled during resize of diskgroup VRVLT_DBS
Wed Mar 18 12:24:36 2015
NOTE: membership refresh pending for group 2/0x2c287964 (VRVLT_DBS)
Wed Mar 18 12:24:39 2015
GMON querying group 2 at 32 for pid 13, osid 5671
SUCCESS: refreshed membership for 2/0x2c287964 (VRVLT_DBS)
ORA-15032: not all alterations performed                                              ================>>>>>>
ORA-15057: specified size of 20480 MB is larger than actual size of 20464 MB

[root@vrvltdb ~]# ls -l /dev/oracleasm/disks
total 0
brw-rw----. 1 oracle dba 8, 193 Mar 31 13:49 VRVLT_DAT_0000  --->  Major Number=8,Minor Number=193
brw-rw----. 1 oracle dba 8, 209 Mar 31 13:50 VRVLT_DAT_0001  --->  Major Number=8,Minor Number=209
brw-rw----. 1 oracle dba 8, 177 Mar 31 13:50 VRVLT_DBS_0000 --->  Major Number=8,Minor Number=177
[root@vrvltdb ~]# cat /proc/partitions
major minor  #blocks  name

  8        0  135266304 sda
  8        1     512000 sda1
  8        2   66595840 sda2
  8       16 1610612736 sdb
  8       32  536870912 sdc
  8       96  188743680 sdg
  8      176  121634816 sdl  ------>   This is much larger than associated the partitioned device of sdl1
  8      177   20955136 sdl1 ----->  VRVLT_DBS_0000 --->  Major Number=8,Minor Number=177 ----> underlying physical device (sd*)  ----->  about 20G  ---->  ORA-15057: specified size of 20480 MB is larger than actual size of 20464 MB
  8       64    7340032 sde
  8       48   33554432 sdd
  8       80   16777216 sdf
  8      144   25165824 sdj
  8      112   33554432 sdh
  8      128   25165824 sdi
  8      192  838860800 sdm
  8      193  838844416 sdm1 ---> VRVLT_DAT_0000  --->  Major Number=8,Minor Number=193 ----> underlying physical device (sd*)
  8      208  838860800 sdn
  8      209  838844416 sdn1 ---> VRVLT_DAT_0001  --->  Major Number=8,Minor Number=209 ----> underlying physical device (sd*)
  8      160  117440512 sdk
252        0  188743680 dm-0  ----> multipathed devices (dm*)
252        1 1610612736 dm-1
252        2  536870912 dm-2
252        3   33554432 dm-3
252        4  117440512 dm-4
252        5   16777216 dm-5
252        6    7340032 dm-6
252        7   25165824 dm-7
252        8   25165824 dm-8
252        9   33554432 dm-9
252       10  838860800 dm-10
252       11  135266304 dm-11
252       12  838860800 dm-12
252       13  121634816 dm-13
252       15     512000 dm-15
252       16   66595840 dm-16
252       18  121618432 dm-18
252       19    2097152 dm-19
252       20    4194304 dm-20
252       21    2097152 dm-21
252       22    2097152 dm-22
252       23   25165824 dm-23
252       24    4194304 dm-24
252       25    6291456 dm-25
252       26    4194304 dm-26
252       27   10485760 dm-27
252       28    5242880 dm-28
252       29   33550336 dm-29
252       30   25161728 dm-30
252       31   25161728 dm-31
252       32   25165824 dm-32
252       33    6291456 dm-33
252       34 1610608640 dm-34
252       35  536866816 dm-35
252       36   33550336 dm-36
252       37    7335936 dm-37
252       38   16773120 dm-38
252       39  188739584 dm-39
252       17  838844416 dm-17
252       14  838844416 dm-14

CAUSE

[root@vrvltdb ~]# cat /etc/sysconfig/oracleasm
#
# This is a configuration file for automatic loading of the Oracle
# Automatic Storage Management library kernel driver.  It is generated
# By running /etc/init.d/oracleasm configure.  Please use that method
# to modify this file
#

# ORACLEASM_ENABLED: 'true' means to load the driver on boot.
ORACLEASM_ENABLED=true

# ORACLEASM_UID: Default user owning the /dev/oracleasm mount point.
ORACLEASM_UID=oracle

# ORACLEASM_GID: Default group owning the /dev/oracleasm mount point.
ORACLEASM_GID=dba

# ORACLEASM_SCANBOOT: 'true' means scan for ASM disks on boot.
ORACLEASM_SCANBOOT=true

# ORACLEASM_SCANORDER: Matching patterns to order disk scanning
ORACLEASM_SCANORDER=""                     -------------------------->  This parameter should be set to ---->  ORACLEASM_SCANORDER="dm"  --->  This forces ASM to scan the multipathed device first (dm*)

# ORACLEASM_SCANEXCLUDE: Matching patterns to exclude disks from scan
ORACLEASM_SCANEXCLUDE=""                  -------------------------->  This parameter should be set to ---->  ORACLEASM_SCANEXCLUDE="sd"  --->  This forces ASM to NOT scan the underlying physical device first (sd*)

# ORACLEASM_USE_LOGICAL_BLOCK_SIZE: 'true' means use the logical block size
# reported by the underlying disk instead of the physical. The default
# is 'false'
ORACLEASM_USE_LOGICAL_BLOCK_SIZE=false

[root@vrvltdb ~]# /sbin/blkid | grep oracleasm
/dev/sdl1: LABEL="VRVLT_DBS_0000" TYPE="oracleasm"
/dev/sdm1: LABEL="VRVLT_DAT_0000" TYPE="oracleasm"
/dev/sdn1: LABEL="VRVLT_DAT_0001" TYPE="oracleasm"
/dev/mapper/VRVLTDB_vrvlt_dbs_0000p1: LABEL="VRVLT_DBS_0000" TYPE="oracleasm"  ---->  multipathed device mapped to dm* device
/dev/mapper/VRVLTDB_vrvlt_dat_0000p1: LABEL="VRVLT_DAT_0000" TYPE="oracleasm"  ---->  multipathed device mapped to dm* device
/dev/mapper/VRVLTDB_vrvlt_dat_0001p1: LABEL="VRVLT_DAT_0001" TYPE="oracleasm"  ---->  multipathed device mapped to dm* device
[root@vrvltdb ~]# /etc/init.d/oracleasm listdisks | xargs /etc/init.d/oracleasm querydisk -d
Disk "VRVLT_DAT_0000" is a valid ASM disk on device [8,193]
Disk "VRVLT_DAT_0001" is a valid ASM disk on device [8,209]
Disk "VRVLT_DBS_0000" is a valid ASM disk on device [8,177]

SOLUTION

 Added the following in the /etc/sysconfig/oracleasm file
  # ORACLEASM_SCANEXCLUDE: Matching patterns to exclude disks from scan
  ORACLEASM_SCANEXCLUDE="sd"

  # ORACLEASM_SCANORDER: Matching patterns to order disk scanning
  ORACLEASM_SCANORDER="dm"