git: hammer2 - stabilization, improvements

[Matthew Dillon]

commit 0924b3f8b02e204754852ec6897879a0373c98aa
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date:   Tue Dec 3 17:52:24 2013 -0800

    hammer2 - stabilization, improvements
    
    * Improve hammer2_io hysteresis by keeping track of a simple activity
      metric when figuring out what to free.  Instead of cleaning out all
      free hammer2_io structures the code now tries to clean out only half
      of them when the hysteresis limit is reached.
    
    * Remove some debug fields, add some debug fields.
    
    * Refactor the memory load flush/wait code.  Instead of tracking the number
      of chain structures we track the number of MODIFIED chain structures,
      and stage early flushes and resource memory use waits based on that.
    
    * Add temporary debug procedure hammer2_chain_assert_not_present() which
      asserts that a chain being created will not collide with a chain already
      present.
    
    * Fix a bug related to freeing non-stale chains that could corrupt the
      flush algorithm.
    
    * Fix bugs related to races between lookups and delete-duplicate operations.
      Races can occur because a delete-duplicate does not lock the chain->above
      core.
    
      This was a nasty one.  A delete-duplicate race can cause a lookup to
      find a DELETE+DUPLICATED chain, but just testing the DUPLICATED bit
      doesn't detect the race.  Instead we have to test whether the bit has
      changed between the spin-locked layer/RBTREE search and the locking of
      the chain that was found.
    
    * Fix a bug in h2ignore_deleted().  When a chain is DUPLICATED, the
      delete_tid must be tested for any bref type.  Not testing this was
      allowing delete-duplicates on inodes to cause chains with the MOVED
      flag set to be left dangling in the in-memory topology and never
      get freed.
    
    * Refactor the flush core a bit, in particular handle a case where
      we were improperly clearing the MOVED bit for a chain which had
      flush-deferred children.
    
    * Remove some unused flags.
    
    * Handle a hardlink shifted-upward race in hammer2_inode_lock_ex().

Summary of changes:
 sys/vfs/hammer2/TODO              |   2 +
 sys/vfs/hammer2/hammer2.h         |  21 ++-
 sys/vfs/hammer2/hammer2_chain.c   | 348 ++++++++++++++++++++++++++++----------
 sys/vfs/hammer2/hammer2_flush.c   | 253 +++++++++++++++++----------
 sys/vfs/hammer2/hammer2_freemap.c |   3 +-
 sys/vfs/hammer2/hammer2_inode.c   | 280 +++++++++++++++---------------
 sys/vfs/hammer2/hammer2_io.c      |  51 ++++--
 sys/vfs/hammer2/hammer2_vfsops.c  |  15 +-
 sys/vfs/hammer2/hammer2_vnops.c   |   8 +
 9 files changed, 636 insertions(+), 345 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/0924b3f8b02e204754852ec6897879a0373c98aa


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