OpenAFS Master Repository branch, openafs-stable-1_6_x, updated. openafs-stable-1_6_11pre1-2-g013e8db

[Gerrit Code Review]

The following commit has been merged in the openafs-stable-1_6_x branch:
commit 013e8db33fbec8b5db4ac5a1ec94a7f5b2afbc45
Author: Marc Dionne <marc.dionne@your-file-system.com>
Date:   Fri Dec 19 10:11:53 2014 -0500

    Unix CM: Avoid using stale DV in afs_StoreAllSegments
    
    It was reported in RT 131976 that on Linux some file
    corruption was observed when doing mmap writes to
    a file substantially larger than the cache size.
    
    osi_VM_StoreAllSegments drops locks and asks the OS to flush
    any dirty pages in the file 's mapping.  This will trigger
    calls into our writepage op, and if the number of dirty
    cache chunks is too high (as will happen for a file larger
    than the cache size), afs_DoPartialWrite will recursively
    call afs_StoreAllSegments and some chunks will be written
    back to the server.  After potentially doing this several
    times, control will return to the original afs_StoreAllSegments.
    
    At that point the data version that was stored before
    osi_VM_StoreAllSegments is no longer correct, leading to
    possible data corruption.
    
    Triggering this bug requires writing a file larger than the
    cache so that partial stores are done, and writing enough
    data to exceed the system's maximum dirty ratio and cause
    it to initiate writeback.
    
    To fix, just wait until after osi_VM_StoreAllSegments to
    look at and store the data version
    
    FIXES 131976
    
    Reviewed-on: http://gerrit.openafs.org/11644
    Tested-by: BuildBot <buildbot@rampaginggeek.com>
    Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
    (cherry picked from commit b22c586bcdf785c489009ab96cbb572181cb9b09)
    
    Change-Id: I32a2f6f32d432fe4a2e21ebd4bb278a9d7e5499f
    Reviewed-on: http://gerrit.openafs.org/11656
    Tested-by: BuildBot <buildbot@rampaginggeek.com>
    Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
    Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>

 src/afs/afs_segments.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

-- 
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