generic: Add test to check for mounting a huge sparse dm device

generic: Add test to check for mounting a huge sparse dm device

Add this test to check for regression which was reported when ext4 bmap
aops was moved to use iomap APIs. jbd2 calls bmap() kernel function
from fs/inode.c which was failing since iomap_bmap() implementation earlier
returned 0 for block addr > INT_MAX.
This regression was fixed with following kernel commit [1]
commit b75dfde1212991b24b220c3995101c60a7b8ae74
("fibmap: Warn and return an error in case of block > INT_MAX")
[1]: https://patchwork.ozlabs.org/patch/1279914

w/o the kernel fix we get below errors and mount fails

[ 1461.988701] run fstests generic/613 at 2020-10-27 19:57:34
[ 1530.406645] ------------[ cut here ]------------
[ 1530.407332] would truncate bmap result
[ 1530.408956] WARNING: CPU: 0 PID: 6401 at fs/iomap/fiemap.c:116 iomap_bmap_actor+0x43/0x50
[ 1530.410607] Modules linked in:
[ 1530.411024] CPU: 0 PID: 6401 Comm: mount Tainted: G        W
<...>
[ 1530.511978] jbd2_journal_init_inode: Cannot locate journal superblock
[ 1530.513310] EXT4-fs (dm-1): Could not load journal inode

Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>