• Ross Zwisler's avatar
    dax: support dirty DAX entries in radix tree · f9fe48be
    Ross Zwisler authored
    Add support for tracking dirty DAX entries in the struct address_space
    radix tree.  This tree is already used for dirty page writeback, and it
    already supports the use of exceptional (non struct page*) entries.
    
    In order to properly track dirty DAX pages we will insert new
    exceptional entries into the radix tree that represent dirty DAX PTE or
    PMD pages.  These exceptional entries will also contain the writeback
    addresses for the PTE or PMD faults that we can use at fsync/msync time.
    
    There are currently two types of exceptional entries (shmem and shadow)
    that can be placed into the radix tree, and this adds a third.  We rely
    on the fact that only one type of exceptional entry can be found in a
    given radix tree based on its usage.  This happens for free with DAX vs
    shmem but we explicitly prevent shadow entries from being added to radix
    trees for DAX mappings.
    
    The only shadow entries that would be generated for DAX radix trees
    would be to track zero page mappings that were created for holes.  These
    pages would receive minimal benefit from having shadow entries, and the
    choice to have only one type of exceptional entry in a given radix tree
    makes the logic simpler both in clear_exceptional_entry() and in the
    rest of DAX.
    Signed-off-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
    Cc: "H. Peter Anvin" <hpa@zytor.com>
    Cc: "J. Bruce Fields" <bfields@fieldses.org>
    Cc: "Theodore Ts'o" <tytso@mit.edu>
    Cc: Alexander Viro <viro@zeniv.linux.org.uk>
    Cc: Andreas Dilger <adilger.kernel@dilger.ca>
    Cc: Dave Chinner <david@fromorbit.com>
    Cc: Ingo Molnar <mingo@redhat.com>
    Cc: Jan Kara <jack@suse.com>
    Cc: Jeff Layton <jlayton@poochiereds.net>
    Cc: Matthew Wilcox <willy@linux.intel.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Dan Williams <dan.j.williams@intel.com>
    Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Hugh Dickins <hughd@google.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    f9fe48be
dax.h 1.56 KB