REVIEW: http://review.gluster.org/9576 (cluster/afr: serialize inode locks) posted (#1) for review on release-3.6 by Pranith Kumar Karampuri (pkarampu)

afr part of the fix is sent for review. Dht patch also needs to be sent out for the complete fix. Assigning to Raghavendra G for now.

COMMIT: http://review.gluster.org/9576 committed in release-3.6 by Raghavendra Bhat (raghavendra) 
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commit 73835a06e87f685354816fb6c2ca4a9918f5e314
Author: Pranith Kumar K <pkarampu>
Date:   Wed Dec 31 15:15:53 2014 +0530

    cluster/afr: serialize inode locks
    
            Backport of http://review.gluster.org/9372
    
    Problem:
    Afr winds inodelk calls without any order, so blocking inodelks
    from two different mounts can lead to dead lock when mount1 gets
    the lock on brick-1 and blocked on brick-2 where as mount2 gets
    lock on brick-2 and blocked on brick-1
    
    Fix:
    Serialize the inodelks whether they are blocking inodelks or
    non-blocking inodelks.
    
            Non-blocking locks also need to be serialized.
    Otherwise there is a chance that both the mounts which issued same
    non-blocking inodelk may endup not acquiring the lock on any-brick.
    Ex:
    Mount1 and Mount2 request for full length lock on file f1.  Mount1 afr may
    acquire the partial lock on brick-1 and may not acquire the lock on brick-2
    because Mount2 already got the lock on brick-2, vice versa. Since both the
    mounts only got partial locks, afr treats them as failure in gaining the locks
    and unwinds with EAGAIN errno.
    
    BUG: 1189023
    Change-Id: If5dd502d9d25d12425749a8efcf08a1423b29255
    Signed-off-by: Pranith Kumar K <pkarampu>
    Reviewed-on: http://review.gluster.org/9576
    Reviewed-by: Krutika Dhananjay <kdhananj>
    Tested-by: Gluster Build System <jenkins.com>
    Reviewed-by: Raghavendra Bhat <raghavendra>

v3.6.7 has the fix