Bug: Over-allocating blocks during mkfs

[lungj]

Summary

When running ext4_mkfs, lwext4 may mark more blocks as free than can actually fit on the device.

Reproducing

make
cd build_generic/fs_test
make
dd if=/dev/zero of=lwext_image bs=1000000 count=200
./lwext4-mkfs -v -i lwext_image -e 4 -b 4096
./lwext4-generic -i lwext_image --sbstat

Actual output shows

blocks_count = 48828
free_blocks_count = 61172
block_size = 4096
block_group_count = 2

Free blocks * block size is over 250MB. The device is only 200MB. The larger the block size, the more the formatted capacity might exceed the physical capacity.

Expected

Whereas with the standard mkfs command on Linux:

dd if=/dev/zero of=ext_image bs=1000000 count=200
mkfs -t ext4 -b 4096 ext_image

We get

blocks_count = 48828
free_blocks_count = 40583
block_size = 4096
block_group_count = 2

Free blocks * block size is about 166B. This fits in the 200MB device.

[kevin-gk]

It's real a bug. Is there a solution?