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  • Jonathan Brassow's avatar
    dm log: userspace add luid to distinguish between concurrent log instances · 7ec23d50
    Jonathan Brassow authored
    Device-mapper userspace logs (like the clustered log) are
    identified by a universally unique identifier (UUID).  This
    identifier is used to associate requests from the kernel to
    a specific log in userspace.  The UUID must be unique everywhere,
    since multiple machines may use this identifier when communicating
    about a particular log, as is the case for cluster logs.
    
    Sometimes, device-mapper/LVM may re-use a UUID.  This is the
    case during pvmoves, when moving from one segment of an LV
    to another, or when resizing a mirror, etc.  In these cases,
    a new log is created with the same UUID and loaded in the
    "inactive" slot.  When a device-mapper "resume" is issued,
    the "live" table is deactivated and the new "inactive" table
    becomes "live".  (The "inactive" table can also be removed
    via a device-mapper 'clear' command.)
    
    The above two issues were colliding.  More than one log was being
    created with the same UUID, and there was no way to d...
    7ec23d50