• W
    ext4: New rec_len encoding for very large blocksizes · 3d0518f4
    Wei Yongjun 提交于
    The rec_len field in the directory entry is 16 bits, so to encode
    blocksizes larger than 64k becomes problematic.  This patch allows us
    to supprot block sizes up to 256k, by using the low 2 bits to extend
    the range of rec_len to 2**18-1 (since valid rec_len sizes must be a
    multiple of 4).  We use the convention that a rec_len of 0 or 65535
    means the filesystem block size, for compatibility with older kernels.
    
    It's unlikely we'll see VM pages of up to 256k, but at some point we
    might find that the Linux VM has been enhanced to support filesystem
    block sizes > than the VM page size, at which point it might be useful
    for some applications to allow very large filesystem block sizes.
    Signed-off-by: NWei Yongjun <yjwei@cn.fujitsu.com>
    Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
    3d0518f4
ext4.h 46.9 KB