OpenAFS Master Repository branch, master, updated. BP-openafs-stable-1_8_x-630-g6c808e0

[Gerrit Code Review]

The following commit has been merged in the master branch:
commit 6c808e05adb0609e02cd61e3c6c4c09eb93c1630
Author: Andrew Deason <adeason@sinenomine.net>
Date:   Thu Jul 13 17:40:36 2017 -0500

    afs: Avoid needless W-locks for afs_FindVCache
    
    The callers of afs_FindVCache must hold at least a read lock on
    afs_xvcache; some hold a shared or write lock (and set IS_SLOCK or
    IS_WLOCK in the given flags). Two callers (afs_EvalFakeStat_int and
    afs_DoBulkStat) currently hold a write lock, but neither of them need
    to.
    
    In the optimal case, where afs_FindVCache finds the given vcache, this
    means that we unnecessarily hold a write lock on afs_xvcache. This can
    impact performance, since afs_xvcache can be a very frequently
    accessed lock (a simple operation like afs_PutVCache briefly holds a
    read lock, for example).
    
    To avoid this, have afs_DoBulkStat hold a shared lock on afs_xvcache,
    upgrading to a write lock when needed. afs_EvalFakeStat_int doesn't
    ever need a write lock at all, so just convert it to a read lock.
    
    Change-Id: I5bd58b9e3a577c9e1ebf1bc3719e65a6c0af5cb8
    Reviewed-on: https://gerrit.openafs.org/12656
    Tested-by: BuildBot <buildbot@rampaginggeek.com>
    Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>

 src/afs/VNOPS/afs_vnop_lookup.c |   17 +++++++++--------
 1 files changed, 9 insertions(+), 8 deletions(-)

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