A volume knob for error reporting when internal errors occur.

This will generate detailed messages & backtraces for filesystem shutdowns, for example.

Current threshold values are:

XFS_ERRLEVEL_OFF:  0
XFS_ERRLEVEL_LOW:  1
XFS_ERRLEVEL_HIGH: 5

Causes certain error conditions to call BUG(). Value is a bitmask;

AND together the tags which represent errors which should cause panics:

XFS_NO_PTAG                0
XFS_PTAG_IFLUSH            0x00000001
XFS_PTAG_LOGRES            0x00000002
XFS_PTAG_AILDELETE         0x00000004
XFS_PTAG_ERROR_REPORT      0x00000008
XFS_PTAG_SHUTDOWN_CORRUPT  0x00000010
XFS_PTAG_SHUTDOWN_IOERROR  0x00000020
XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040