LU-9796 kernel: improve metadata performaces for RHEL7

LU-9796 kernel: improve metadata performaces for RHEL7

Port following upstream patch for RHEL7:

commit de92c8caf16ca84926fa31b7a5590c0fb9c0d5ca
Author: Jan Kara <jack@suse.cz>
Date:   Mon Jun 8 12:46:37 2015 -0400

    jbd2: speedup jbd2_journal_get_[write|undo]_access()

    jbd2_journal_get_write_access() and jbd2_journal_get_create_access() are
    frequently called for buffers that are already part of the running
    transaction - most frequently it is the case for bitmaps, inode table
    blocks, and superblock. Since in such cases we have nothing to do, it is
    unfortunate we still grab reference to journal head, lock the bh, lock
    bh_state only to find out there's nothing to do.

    Improving this is a bit subtle though since until we find out journal
    head is attached to the running transaction, it can disappear from under
    us because checkpointing / commit decided it's no longer needed. We deal
    with this by protecting journal_head slab with RCU. We still have to be
    careful about journal head being freed & reallocated within slab and
    about exposing journal head in consistent state (in particular
    b_modified and b_frozen_data must be in correct state before we allow
    user to touch the buffer).

    Signed-off-by: Jan Kara <jack@suse.cz>
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
From 087ffd4eae9929afd06f6a709861df3c3508492a Mon Sep 17 00:00:00 2001
Date: Fri, 4 Dec 2015 12:29:28 -0500
Subject: [PATCH] jbd2: fix null committed data return in undo_access

     introduced jbd2_write_access_granted() to improve write|undo_access
     speed, but missed to check the status of b_committed_data which caused
     a kernel panic on ocfs2.
     ...

     Fixes: de92c8caf16c("jbd2: speedup jbd2_journal_get_[write|undo]_access()")
     Cc: <stable@vger.kernel.org>
     Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
     Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This patches improve 10% of file create, 17% of file lustre unlink
performances

Change-Id: I8082be396209d8f658e3265cedf32670e15a53f5
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-on: https://review.whamcloud.com/28276
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Reviewed-by: Li Xi <lixi@ddn.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>