OpenAFS Master Repository branch, master, updated. openafs-devel-1_5_76-4278-g0abf5fc

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit 0abf5fcbe8a0367a91224fa50480e78f0e6b02e4
Author: Marc Dionne <marc.dionne@your-file-system.com>
Date:   Mon May 5 13:33:10 2014 -0400

    Linux: Drop PageReclaim AOP_WRITEPAGE_ACTIVATE case
    
    The exit case here seems to have been added to avoid recursion into
    the writeback code and eventual deadlock (see RT #15239).  One issue
    is that the PageReclaim check can trigger in code paths that don't
    deal with the AOP_WRITEPAGE_ACTIVATE code correctly, leading to EIO
    errors when multiple threads are doing large mmap writes and memory
    pressure is sufficient to trigger reclaim.
    
    The check could be improved to check wbc.for_reclaim which seems to
    indicate more reliably when it is safe to return ACTIVATE, but given
    that the CPageWrite flag already provides more targeted recursion
    prevention, it seems safer to just drop this special case.
    
    Note that many kernel filesystems used to have a similar check mainly
    to prevent excessive stack usage, but as more recent kernels have
    moved away from doing any writeback during direct reclaim this is a
    case that should no longer occur.  Partly as a result of this there
    are very few users of AOP_WRITEPAGE_ACTIVATE left in the kernel,
    which may be a motivation to find a better mechanism for OpenAFS
    eventually.
    
    This has been shown to help avoid EIO errors with multiple processes
    doing intensive mmap writing.
    
    Thanks to Yadav Yadavendra for identifying the issue and providing
    extensive analysis and testing.
    
    Change-Id: I88d9ef6e6e7a8f666f82c5ca481254839c2ba1e5
    Reviewed-on: http://gerrit.openafs.org/11125
    Reviewed-by: D Brashear <shadow@your-file-system.com>
    Tested-by: BuildBot <buildbot@rampaginggeek.com>

 src/afs/LINUX/osi_vnodeops.c |    5 -----
 1 files changed, 0 insertions(+), 5 deletions(-)

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