On rawhide (4.7.0-0.rc0.git5.1.fc25.x86_64), the kernel's 'struct inode' has changed so that 'i_mutex' no longer exists. Starting with the following commit, a set of wrapper functions has been added in preparation for the removal of switching that mutex to a rwsem.

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commit 5955102c9984fa081b2d570cfac75c97eecf8f3b
Author: Al Viro <viro@zeniv.linux.org.uk>
Date:   Fri Jan 22 15:40:57 2016 -0500

    wrappers for ->i_mutex access
    
    parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
    inode_foo(inode) being mutex_foo(&inode->i_mutex).
    
    Please, use those for access to ->i_mutex; over the coming cycle
    ->i_mutex will become rwsem, with ->lookup() done with it held
    only shared.
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The runtime should be updated to handle this change.