cvs commit: src/sys/kern vfs_bio.c

[Matthew Dillon]

dillon      2003/10/07 17:10:56 PDT

  Modified files:
    sys/kern             vfs_bio.c 
  Log:
  Disable background bitmap writes.  They appear to cause at least two race
  conditions:  First, on MP systems even an LK_NOWAIT lock may block,
  invalidating flags checks done just prior to the lock attempt.  Second, on
  both MP and UP systems, the original buffer (origbp) may be modified during
  the completion of a background write without its lock being held and these
  modifications can race against mainline code that is also modifying the same
  buffer with the lock held.
  
  Eventually the problem background bitmap writes solved will be solved more
  generally by implementing page COWing durign device I/O to avoid stalls on
  pages undergoing write I/O.
  
  Revision  Changes    Path
  1.15      +12 -1     src/sys/kern/vfs_bio.c