Why did GFS2 filesystem withdraw with "fatal: invalid metadata block" and "function = get_leaf, file = fs/gfs2/dir.c, line = 701" when trying to mount on RHEL 5.4?

Issue

• Getting "input/output IO error" messages, when trying to cd into the mountpoint or to any others directories underneath it.
• The df command on the mountpoint was just displaying ???? marks.
• Unable to umount GFS2 filesystem.
• The following error messages were found in /var/log/messages:

Feb 21 21:32:19 <hostname> kernel: GFS2: fsid=va2xpcpb01_02:query.0: fatal: invalid metadata block
Feb 21 21:32:19 <hostname> kernel: GFS2: fsid=va2xpcpb01_02:query.0:   bh = 0 (magic number)
Feb 21 21:32:19 <hostname> kernel: GFS2: fsid=va2xpcpb01_02:query.0:   function = get_leaf, file = fs/gfs2/dir.c, line = 701
Feb 21 21:32:19 <hostname> kernel: GFS2: fsid=va2xpcpb01_02:query.0: about to withdraw this file system
Feb 21 21:32:19 <hostname> kernel: GFS2: fsid=va2xpcpb01_02:query.0: telling LM to withdraw
Feb 21 21:32:19 <hostname> kernel: GFS2: fsid=va2xpcpb01_02:query.0: gfs2_delete_inode: -5
Feb 21 21:32:20 <hostname> kernel: GFS2: fsid=va2xpcpb01_02:query.0: withdrawn
Feb 21 21:32:20 <hostname> kernel:
Feb 21 21:32:20 <hostname> kernel: Call Trace:
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff88587526>] :gfs2:gfs2_lm_withdraw+0xc1/0xd0
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff80063ae7>] __wait_on_bit+0x60/0x6e
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff80015008>] sync_buffer+0x0/0x3f
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff80063b61>] out_of_line_wait_on_bit+0x6c/0x78
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff8009dbd6>] wake_bit_function+0x0/0x23
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff8001a370>] submit_bh+0x10a/0x111
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff8859a68f>] :gfs2:gfs2_meta_check_ii+0x2c/0x38
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff8857d51c>] :gfs2:get_leaf+0x6b/0xa8
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff8857ed52>] :gfs2:gfs2_dir_read+0x1c8/0x535
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff80025256>] filldir+0x0/0xb7
Feb 21 21:32:20 <hostname> kernel:  [<ffffffff80025256>] filldir+0x0/0xb7
Feb 21 21:32:21 <hostname> kernel:  [<ffffffff8858eb0b>] :gfs2:gfs2_readdir+0x6b/0x8f
Feb 21 21:32:21 <hostname> kernel:  [<ffffffff8858eae0>] :gfs2:gfs2_readdir+0x40/0x8f
Feb 21 21:32:21 <hostname> kernel:  [<ffffffff80025256>] filldir+0x0/0xb7
Feb 21 21:32:21 <hostname> kernel:  [<ffffffff80034c9a>] vfs_readdir+0x77/0xa9
Feb 21 21:32:21 <hostname> kernel:  [<ffffffff80038542>] sys_getdents+0x75/0xbd
Feb 21 21:32:21 <hostname> kernel:  [<ffffffff8005dde9>] error_exit+0x0/0x84
Feb 21 21:32:21 <hostname> kernel:  [<ffffffff8005d116>] system_call+0x7e/0x83