xfstests: add a helper to get the minimum dio size

Various tests opencode checks to find out the minimum support direct I/O
size.  Replace those with a generic helper that handles network filesystems as
well.  Also remove the Linux 2.4 workaround we had in once place.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Rich Johnston <rjohnston@sgi.com>

tests/generic/091

@@ -54,11 +54,7 @@ run_fsx()
 }
 
 psize=`$here/src/feature -s`
-bsize=`blockdev --getss $TEST_DEV`
-kernel=`uname -r  | sed -e 's/\(2\..\).*/\1/'`
-
-# 2.4 Linux kernels support bsize aligned direct I/O only
-[ "$HOSTOS" = "Linux" -a "$kernel" = "2.4" ] && bsize=$psize
+bsize=`_min_dio_alignment $TEST_DEV`
 
 # fsx usage:
 # 

tests/generic/240

@@ -60,7 +60,7 @@ rm -f $seqres.full
 
 rm -f $TEST_DIR/aiodio_sparse
 
-logical_block_size=`blockdev --getss $TEST_DEV`
+logical_block_size=`_min_dio_alignment $TEST_DEV`
 fs_block_size=`stat -f $TEST_DIR | grep "Block size:" | awk '{print $3}'`
 
 if [ $fs_block_size -le $logical_block_size ]; then

tests/generic/263

@@ -54,7 +54,7 @@ run_fsx()
 }
 
 psize=`$here/src/feature -s`
-bsize=`blockdev --getss $TEST_DEV`
+bsize=`_min_dio_alignment $TEST_DEV`
 
 run_fsx -N 10000  -o 8192   -l 500000 -r PSIZE -t BSIZE -w BSIZE -Z
 run_fsx -N 10000  -o 128000 -l 500000 -r PSIZE -t BSIZE -w BSIZE -Z