The x86 assembly instructures for bit test-and-set, test-and-clear,
etc., interpret the bit number as a 32-bit signed number, which is
problematic in order to support filesystems > 8TB.
Added new inline functions (in C) to implement a
ext2fs_fast_set/clear_bit() that does not return the old value of the
bit, and use it for the fast block/bitmap functions.
Added a regression test suite to test the low-level bit operations
functions to make sure they work correctly.
Note that a bitmap can address 2**32 blocks requires 2**29 bytes, or
512 megabytes. E2fsck requires 3 (and possibly 4 block bitmaps),
which means that the block bitmaps can require 2GB all by themselves,
and this doesn't include the 4 or 5 inode bitmaps (which assuming an
8k inode ratio, will take 256 megabytes each). This means that it's
more likely that a filesystem check of a filesystem greater than 2**31
blocks will fail if the e2fsck is dynamically linked (since the shared
libraries can consume a substantial portion of the 3GB address space
available to x86 userspace applications). Even if e2fsck is
statically linked, for a badly damaged filesystem, which may require
additional block and/or inode bitmaps, I am not sure e2fsck will
succeed in all cases.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Theodore Ts'o