[Bugs] [Bug 1414242] [whql][virtio-block+glusterfs]"Disk Stress" and " Disk Verification" job always failed on win7-32/win2012/win2k8R2 guest

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1414242



--- Comment #2 from Worker Ant <bugzilla-bot at gluster.org> ---
COMMIT: https://review.gluster.org/7447 committed in master by Raghavendra G
(rgowdapp at redhat.com) 
------
commit 2ff39c5cbea6fbda0d7a442f55e6dc2a72efb171
Author: Raghavendra G <rgowdapp at redhat.com>
Date:   Fri Apr 11 15:58:47 2014 +0530

    performance/read-ahead: prevent stale data being returned to application.

    Assume that fd is shared by two application threads/processes.

    T0 read is triggered from app-thread t1 and read call passes through
       write-behind.
    T1 app-thread t2 issues a write. The page on which read from t1 is
       waiting is marked stale
    T2 write-behind caches write and indicates to application as write
       complete.
    T3 app-thread t2 issues read to same region. Since, there is already a
       page for that region (created as part of read at T0), this read
       request waits on that page to be filled (though it is stale, which
       is a bug).
    T4 read (triggered at T0) completes from brick (with write still
       pending). Now both read requests from t1 and t2 are served this data
       (though data is stale from app-thread t2's perspective - which is a
       bug)
    T5 write is flushed to brick by write-behind.

    Fix is to not to serve data from a stale page, but instead initiate a
    fresh read to back-end.

    Change-Id: Id6af733464fa41bb4e81fd29c7451c73d06453fb
    BUG: 1414242
    Signed-off-by: Raghavendra G <rgowdapp at redhat.com>
    Reviewed-on: https://review.gluster.org/7447
    Smoke: Gluster Build System <jenkins at build.gluster.org>
    CentOS-regression: Gluster Build System <jenkins at build.gluster.org>
    Reviewed-by: Csaba Henk <csaba at redhat.com>
    NetBSD-regression: NetBSD Build System <jenkins at build.gluster.org>
    Reviewed-by: Zhou Zhengping <johnzzpcrystal at gmail.com>
    Reviewed-by: Amar Tumballi <amarts at redhat.com>

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