See
ext2_new_inode() in `fs/ext2/ialloc.c'.
More accurately, the test is
based on whether or not the EXT2_COMPRBLK_FL flag is set for the
file. In some, rare, circumstances, the EXT2_COMPRBLK_FL flag
can still be set even when no clusters of that
file are compressed.
At present there is a real reason for some people to use larger blocks because of a limitation in e2compr: at present, the cluster bitmap is stored uncompressed, in no more than one filesystem block. With a 1024-byte blocksize, only the first 256MB of a file can be compressed; the rest must be stored in uncompressed form. With 4096-byte blocks, the first gigabyte (or thereabouts; actually 1.5MB less than a gigabyte) can be compressed. This may change soon, but the change I have in mind may break some existing installations, so I'm hesitant.
This document was generated on 16 December 1997 using the texi2html translator version 1.51.