bzr push into mysql-5.6 branch (annamalai.gurusami:4808 to 4809)

[Annamalai Gurusami]

 4809 Annamalai Gurusami	2012-12-20 [merge]
      Null merge from mysql-5.5 to mysql-5.6. 

 4808 Annamalai Gurusami	2012-12-20
      Bug #14556349 RENAME OF COMPRESSED TABLE AND INSERT BUFFER MERGE CAUSE
      HANG
      
      Problem Statement:
      
      When the operation RENAME TABLE is about rename the tablespace of the
      table, it will stop all i/o operations on the tablespace temporarily.
      For this the fil_space_t::stop_ios member is used.
      
      Once the fil_space_t::stop_ios member is set to TRUE in the RENAME
      TABLE operation, it is expected that no new i/o operation will be done
      on the tablespace and all pending i/o operation can be completed on
      the tablespace.
      
      If the pending i/o operations initiate any new i/o operations then
      there will be deadlock.  The RENAME TABLE operation will be waiting
      for pending i/o on the tablespace to be completed, and the pending i/o
      operations will be waiting on the RENAME TABLE operation to set the
      file_space_t::stop_ios flag to be set to FALSE.
      
      But in the given scenario the pending i/o operations did not initiate
      new i/o.  But they where still unnecessarily checking the
      fil_space_t::stop_ios flag.  This resulted in deadlock.
      
      Solution:
      
      I noticed that this deadlock happens in fil_space_get_size() and
      fil_space_get_zip_size() in the i/o threads.  These functions check
      the stop_ios flag even when no i/o will be initiated.  I modified
      these functions to ensure that they check the stop_ios flag only when
      they will be initiating an i/o operation.  This solves the problem.
      
      rb://1635 (mysql-5.5)
      rb://1660 (mysql-trunk) approved by Inaam, Jimmy, and ima.

    modified:
      storage/innobase/fil/fil0fil.cc
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