• Jan Kara's avatar
    dax: Make huge page handling depend of CONFIG_BROKEN · 348e967a
    Jan Kara authored
    Currently the handling of huge pages for DAX is racy. For example the
    following can happen:
    CPU0 (THP write fault)			CPU1 (normal read fault)
    __dax_pmd_fault()			__dax_fault()
      get_block(inode, block, &bh, 0) -> not mapped
    					get_block(inode, block, &bh, 0)
    					  -> not mapped
      if (!buffer_mapped(&bh) && write)
        get_block(inode, block, &bh, 1) -> allocates blocks
      truncate_pagecache_range(inode, lstart, lend);
    This results in data corruption since process on CPU1 won't see changes
    into the file done by CPU0.
    The race can happen even if two normal faults race however with THP the
    situation is even worse because the two faults don't operate on the same
    entries in the radix tree and we want to use these entries for
    serialization. So make THP support in DAX code depend on CONFIG_BROKEN
    for now.
    Signed-off-by: default avatarJan Kara <jack@suse.cz>
    Signed-off-by: default avatarRoss Zwisler <ross.zwisler@linux.intel.com>
Kconfig 6.92 KB