RHEL6: CIFS shares unavailable after upstream fileserver failure

Issue

• A RHEL6 server CIFS mountpoint hangs when a Windows server suffers a failure. The following errors are seen on /var/log/messages:

Oct 12 16:59:27 server kernel: CIFS VFS: Server fileservercorp01 has not responded in 300 seconds. Reconnecting.
Oct 13 00:29:08 server kernel: INFO: task bash:30497 blocked for more than 120 seconds.
Oct 13 00:29:08 server kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Oct 13 00:29:08 server kernel: bash          D 0000000000000013     0 30497  30321 0x00000080
Oct 13 00:29:08 server kernel: ffff8807fd8c5ab8 0000000000000086 0000000000000000 0000000000000003
Oct 13 00:29:08 server kernel: 0000000000000001 0000000000000282 ffff8807fd8c5a68 ffff880f7075d7b0
Oct 13 00:29:08 server kernel: ffff880815aebaf8 ffff8807fd8c5fd8 000000000000fb88 ffff880815aebaf8
Oct 13 00:29:08 server kernel: Call Trace:
Oct 13 00:29:08 server kernel: [<ffffffff814ff42e>] __mutex_lock_slowpath+0x13e/0x180
Oct 13 00:29:08 server kernel: [<ffffffff811fd1b9>] ? find_nls+0x59/0x100
Oct 13 00:29:08 server kernel: [<ffffffff814ff2cb>] mutex_lock+0x2b/0x50
Oct 13 00:29:08 server kernel: [<ffffffffa02a940a>] cifs_reconnect_tcon+0x15a/0x340 [cifs]
Oct 13 00:29:08 server kernel: [<ffffffff81114e6a>] ? generic_file_buffered_write+0x1da/0x2e0
Oct 13 00:29:08 server kernel: [<ffffffff81072547>] ? current_fs_time+0x27/0x30
Oct 13 00:29:08 server kernel: [<ffffffffa02a96b9>] smb_init+0x39/0x70 [cifs]
Oct 13 00:29:08 server kernel: [<ffffffffa02af84a>] CIFSSMBQPathInfo+0x5a/0x2d0 [cifs]
Oct 13 00:29:08 server kernel: [<ffffffffa02c4b37>] cifs_get_inode_info+0x3c7/0x650 [cifs]
Oct 13 00:29:08 server kernel: [<ffffffffa02bc567>] ? build_path_from_dentry+0x1a7/0x230 [cifs]
Oct 13 00:29:08 server kernel: [<ffffffffa02c52b7>] cifs_revalidate_dentry+0x1a7/0x280 [cifs]
Oct 13 00:29:08 server kernel: [<ffffffff8118bbc2>] ? user_path_at+0x62/0xa0
Oct 13 00:29:08 server kernel: [<ffffffffa02c53d4>] cifs_getattr+0x44/0xe0 [cifs]
Oct 13 00:29:08 server kernel: [<ffffffff81180781>] vfs_getattr+0x51/0x80
Oct 13 00:29:08 server kernel: [<ffffffff81180810>] vfs_fstatat+0x60/0x80
Oct 13 00:29:08 server kernel: [<ffffffff8118095b>] vfs_stat+0x1b/0x20
Oct 13 00:29:08 server kernel: [<ffffffff81180984>] sys_newstat+0x24/0x50
Oct 13 00:29:08 server kernel: [<ffffffff810d6ce2>] ? audit_syscall_entry+0x272/0x2a0
Oct 13 00:29:08 server kernel: [<ffffffff8100b0f2>] system_call_fastpath+0x16/0x1b