• Artem Bityutskiy's avatar
    vfs: kill write_super and sync_supers · f0cd2dbb
    Artem Bityutskiy authored
    Finally we can kill the 'sync_supers' kernel thread along with the
    '->write_super()' superblock operation because all the users are gone.
    Now every file-system is supposed to self-manage own superblock and
    its dirty state.
    The nice thing about killing this thread is that it improves power management.
    Indeed, 'sync_supers' is a source of monotonic system wake-ups - it woke up
    every 5 seconds no matter what - even if there were no dirty superblocks and
    even if there were no file-systems using this service (e.g., btrfs and
    journalled ext4 do not need it). So it was wasting power most of the time. And
    because the thread was in the core of the kernel, all systems had to have it.
    So I am quite happy to make it go away.
    Interestingly, this thread is a left-over from the pdflush kernel thread which
    was a self-forking kernel thread responsible for all the write-back in old
    Linux kernels. It was turned into per-block device BDI threads, and
    'sync_supers' was a left-over. Thus, R.I.P, pdflush as well.
    Signed-off-by: default avatarArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
backing-dev.h 10.2 KB