common: Introduce get_block_size() helper

Currently many tests and other functions uses it's own way to get block
size of the file system. Introduce get_block_size(), a generic way to
get block size of mounted file system and use that instead.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/generic/240

@@ -62,7 +62,7 @@ rm -f $seqres.full
 rm -f $TEST_DIR/aiodio_sparse
 
 logical_block_size=`_min_dio_alignment $TEST_DEV`
-fs_block_size=`stat -f $TEST_DIR | grep "Block size:" | awk '{print $3}'`
+fs_block_size=`get_block_size $TEST_DIR`
 file_size=$((8 * $fs_block_size))
 
 if [ $fs_block_size -le $logical_block_size ]; then

tests/generic/256

@@ -171,7 +171,7 @@ _scratch_mount
 # Test must be able to write files with non-root permissions
 chmod 777 $SCRATCH_MNT
 
-block_size=`stat -f $SCRATCH_DEV | grep "Block size" | cut -d " " -f3`
+block_size=`get_block_size $SCRATCH_MNT`
 _test_full_fs_punch $(( $block_size * 2 )) $block_size 500 $SCRATCH_MNT/252.$$ $block_size
 
 status=0 ; exit

tests/generic/308

@@ -49,7 +49,7 @@ _require_test
 rm -f $seqres.full
 echo "Silence is golden"
 
-block_size=`stat -f -c %s $TEST_DIR`
+block_size=`get_block_size $TEST_DIR`
 
 # On unpatched ext4, if an extent exists which includes the block right
 # before the maximum file offset, and the block for the maximum file offset