ext4fs_allocate_blocks() always allocates at least one block for a file.
If the file size is zero, this causes total_remaining_blocks to
underflow, which then causes an apparent hang while 2^32 blocks are
allocated.
To solve this, check that total_remaining_blocks is non-zero as part of
the loop condition (i.e. before each loop) rather than at the end of
the loop.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
d018028055