git: DragonFly_RELEASE_3_0 kernel -- ffs: Soft updates locking fixes

[Venkatesh Srinivas <vsrinivas@xxxxxxxxxxxxxxxxxxxxxxx>]

commit df0bdd59624ebea358b2f3922d0e1990d83c686c
Author: Venkatesh Srinivas <me@endeavour.zapto.org>
Date:   Sat Apr 21 20:05:06 2012 -0700

    kernel -- ffs: Soft updates locking fixes
    
    1) Do not take mplock in bioops callbacks; the lock was no longer synchronizing
       against mainline code.
    
    2) Do not hold softdep lock around bwillinode()
    
    3) Take softdep lock in softdep_process_worklist bioops callback. This callback
       was previously using the mplock for synchronization (insufficiently!)
    
    4) Modify process_worklist_item to expect the softdep lock to be held on
       entry and release it at appropriate times.
    
    Prevents a panic seen when running fsstress on a UFS+softdep fs, where fsync
    finds a null buffer on vnode trees. This arose from a front-end/back-end
    race in softdep_process_worklist.

Summary of changes:
 sys/vfs/ufs/ffs_softdep.c |   33 +++++++++------------------------
 1 files changed, 9 insertions(+), 24 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/df0bdd59624ebea358b2f3922d0e1990d83c686c


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