e2freefrag: use 64-bit rbtree bitmaps

Enable the use of 64-bit bitmaps, so e2freefrag will work on file
systems with the 64-bit feature enabled.  In addition, enable the
rbtree-based bitmaps, which significantly saves the amount of memory
required (from 97 megs to 1.7 megs for an empty 3T file system) at the
cost of additional CPU overhead (but we will claw back some of the
additional CPU overhead in the next commit).

Addresses-Google-Bug: 7269948

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
libext2fs: optimize rb_test_bit

Optimize testing for a bit in an rbtree-based bitmap for the case
where the calling application is scanning through the bitmap
sequentially.  Previously, we did this for a set of bits which were
inside an allocated extent, but we did not optimize the case where
there was a large number of bits after an allocated extents which were
not in use.

             1111111111111110000000000000000000
             ^ optimized    ^not optimized

In my tests of a roughly half-filled file system, the run time of
e2freefrag was halved, and the cpu time spent in userspace was during
e2fsck's pass 5 was reduced by a factor of 30%.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
libext2fs: remove pointless indirection in rbtree bitmaps

The code was previously allocating a single 4 or 8 byte pointer for
the rcursor and wcursor fields in the ext2fs_rb_private structure;
this added two extra memory allocations (which could fail), and extra
indirections, for no good reason.  Removing the extra indirection also
makes the code more readable, so it's all upside and no downside.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
libext2fs: further optimize rb_test_bit

Profiling shows that rb_test_bit() is now calling ext2fs_rb_next() a
lot, and this function is now the hot spot when running e2freefrag.
If we cache the results of ext2fs_rb_next(), we can eliminate those
extra calls, which further speeds up both e2freefrag and e2fsck by
reducing the amount of CPU time spent in userspace.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Fix makefiles to compile e2freefrag with profiling

Also fix a bug caused by a stray continuation backslash which caused
the e2fsck/Makefile to fail when profiling is enabled.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
e2fsck: only consult inode_dir_map if needed in pass4

In e2fsck_pass4(), we were consulting inode_dir_map using
ext2fs_test_inode_bitmap2() for every single inode in the file system.
However, there were many cases where we never needed the result of the
test --- most notably if the inode is not in use.

I was a bit surprised that GCC 4.7 with CFLAGS set to "-g -O2" wasn't
able to optimize this out for us, but here is the pass 4 timing for an
empty 3T file system before this patch:

Pass 4: Memory used: 672k/772k (422k/251k), time:  3.67/ 3.66/ 0.00

and afterwards, we see a 43% improvement:

Pass 4: Memory used: 672k/772k (422k/251k), time:  2.09/ 2.08/ 0.00

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Merge branch 'maint' into next

Conflicts:
	lib/ext2fs/blkmap64_rb.c