• Arnd Bergmann's avatar
    ufs: remove the BKL · 788257d6
    Arnd Bergmann authored
    This introduces a new per-superblock mutex in UFS to replace
    the big kernel lock. I have been careful to avoid nested
    calls to lock_ufs and to get the lock order right with
    respect to other mutexes, in particular lock_super.
    
    I did not make any attempt to prove that the big kernel
    lock is not needed in a particular place in the code,
    which is very possible.
    
    The mutex has a significant performance impact, so it is only
    used on SMP or PREEMPT configurations.
    
    As Nick Piggin noticed, any allocation inside of the lock
    may end up deadlocking when we get to ufs_getfrag_block
    in the reclaim task, so we now use GFP_NOFS.
    Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
    Tested-by: default avatarNick Bowler <nbowler@elliptictech.com>
    Cc: Evgeniy Dushistov <dushistov@mail.ru>
    Cc: Nick Piggin <npiggin@gmail.com>
    788257d6
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