• Matias Bjørling's avatar
    lightnvm: core on-disk initialization · e3eb3799
    Matias Bjørling authored
    An Open-Channel SSD shall be initialized before use. To initialize, we
    define an on-disk format, that keeps a small set of metadata to bring up
    the media manager on top of the device.
    
    The initial step is introduced to allow a user to format the disks for a
    given media manager. During format, a system block is stored on one to
    three separate luns on the device. Each lun has the system block
    duplicated. During initialization, the system block can be retrieved and
    the appropriate media manager can initialized.
    
    The on-disk format currently covers (struct nvm_system_block):
    
     - Magic value "NVMS".
     - Monotonic increasing sequence number.
     - The physical block erase count.
     - Version of the system block format.
     - Media manager type.
     - Media manager superblock physical address.
    
    The interface provides three functions to manage the system block:
    
     int nvm_init_sysblock(struct nvm_dev *, struct nvm_sb_info *)
     int nvm_get_sysblock(struct nvm *dev, struct nvm_sb_info *)
     int nvm_update_sysblock(struct nvm *dev, struct nvm_sb_info *)
    
    Each implement a part of the logic to manage the system block. The
    initialization creates the first system blocks and mark them on the
    device. Get retrieves the latest system block by scanning all pages in
    the associated system blocks. The update sysblock writes new metadata
    and allocates new block if necessary.
    Signed-off-by: default avatarMatias Bjørling <m@bjorling.me>
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
    e3eb3799
core.c 23.1 KB