• Ryusuke Konishi's avatar
    nilfs2: add routines to redirect access to buffers of DAT file · b1f6a4f2
    Ryusuke Konishi authored
    During garbage collection (GC), DAT file, which converts virtual block
    number to real block number, may return disk block number that is not
    yet written to the device.
    
    To avoid access to unwritten blocks, the current implementation stores
    changes to the caches of GCDAT during GC and atomically commit the
    changes into the DAT file after they are written to the device.
    
    This patch, instead, adds a function that makes a copy of specified
    buffer and stores it in nilfs_shadow_map, and a function to get the
    backup copy as needed (nilfs_mdt_freeze_buffer and
    nilfs_mdt_get_frozen_buffer respectively).
    
    Before DAT changes block number in an entry block, it makes a copy and
    redirect access to the buffer so that address conversion function
    (i.e. nilfs_dat_translate) refers to the old address saved in the
    copy.
    
    This patch gives requisites for such redirection.
    Signed-off-by: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
    b1f6a4f2
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