• Ross Zwisler's avatar
    ext2: Add locking for DAX faults · 5726b27b
    Ross Zwisler authored
    Add locking to ensure that DAX faults are isolated from ext2 operations
    that modify the data blocks allocation for an inode.  This is intended to
    be analogous to the work being done in XFS by Dave Chinner:
    
    http://www.spinics.net/lists/linux-fsdevel/msg90260.html
    
    Compared with XFS the ext2 case is greatly simplified by the fact that ext2
    already allocates and zeros new blocks before they are returned as part of
    ext2_get_block(), so DAX doesn't need to worry about getting unmapped or
    unwritten buffer heads.
    
    This means that the only work we need to do in ext2 is to isolate the DAX
    faults from inode block allocation changes.  I believe this just means that
    we need to isolate the DAX faults from truncate operations.
    
    The newly introduced dax_sem is intended to replicate the protection
    offered by i_mmaplock in XFS.  In addition to truncate the i_mmaplock also
    protects XFS operations like hole punching, fallocate down, extent
    manipulation IOCTLS like xfs_ioc_space() and extent swapping.  Truncate is
    the only one of these operations supported by ext2.
    Signed-off-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
    Signed-off-by: default avatarJan Kara <jack@suse.com>
    5726b27b
ext2.h 27.8 KB