git: kernel - Hold vm_token() for certain buf/bio/vm_page interactions

Matthew Dillon dillon at
Sat Nov 27 22:45:26 PST 2010

commit 763e6ed1f4de4043907d79652371ce3303e9bebc
Author: Matthew Dillon <dillon at>
Date:   Sat Nov 27 22:28:52 2010 -0800

    kernel - Hold vm_token() for certain buf/bio/vm_page interactions
    * Hold the vm_token when messing around with page valid and dirty bits
      in buffer cache operations.  Such race conditions are possible but would
      be very rare.
    * Fix inconsistent use of bio2.bio_offset when swapcache intercepts an
      I/O operation.  When this case occurs the normal filesystem VOP_STRATEGY
      function will not be called and any assumption that bio2.bio_offset
      will represent a block device offset will be invalid.
      To deal with this case swapcache will re-set bio_offset to NOOFFSET.
      Filesystems use this value to determine that no block device offset
      has been cached for a logical file block.
    Reported-by: Jan Lentfer <Jan.Lentfer at> (bio_offset issue)

Summary of changes:
 sys/kern/vfs_bio.c |   47 +++++++++++++++++++++++++++++++++++++++--------
 1 files changed, 39 insertions(+), 8 deletions(-)

DragonFly BSD source repository

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