[Bugs] [Bug 1349879] AFR winds a few reads of a file in metadata split-brain.

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1349879



--- Comment #2 from Vijay Bellur <vbellur at redhat.com> ---
COMMIT: http://review.gluster.org/14790 committed in release-3.8 by Pranith
Kumar Karampuri (pkarampu at redhat.com) 
------
commit cae76bad7a31c60a3bf17fa1e5005ec5975bf91e
Author: Ravishankar N <ravishankar at redhat.com>
Date:   Fri Feb 5 15:10:06 2016 +0530

    afr:Don't wind reads for files in metadata split-brain

    Backport of http://review.gluster.org/#/c/13389/

    Problem: For a read on  a file in metadata split-brain:
    1.lookup_done resets event_generation to zero.
    2. readv is issued, goes to inode refresh due to mismatching event_gen.
    3. After refresh is successful, we update event_generation, data and
    metdata readable.
    3. We then call afr_read_txn_refresh_done() which in turn calls
    afr_inode_get_readable() but doesn't check for EIO. So afr_readv_wind
    is called with local->readable (which is populated with data_readable),
    thus winding the read to a brick.
    4. Also, further parallel reads that come directly go to the wind path
    because there is no inode_refresh needed.

    Fix:
    1.For any afr_read_txn(), readable must be an intersection of data and
metadata
    readable.
    2.Check for EIO in afr_read_txn_refresh_done().

    Change-Id: I22dd221fdfaf96d7aced2f474e28ed1337d69f0e
    BUG: 1349879
    Signed-off-by: Ravishankar N <ravishankar at redhat.com>
    (cherry picked from commit 7a1c1e2904701496968ed14b6d7479fb706c3188)
    Reviewed-on: http://review.gluster.org/14790
    Smoke: Gluster Build System <jenkins at build.gluster.org>
    NetBSD-regression: NetBSD Build System <jenkins at build.gluster.org>
    CentOS-regression: Gluster Build System <jenkins at build.gluster.org>
    Reviewed-by: Pranith Kumar Karampuri <pkarampu at redhat.com>

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