Reduce size of zvol and enforce 4k blocksize in zvol tests

32-bit builders in the buildbot are having trouble completing
their ENOSPC testing in less than the timeout. Reduce the
zvol size and use a 4k block size to reduce read-modify-writes
which are particularly expensive on 32-bit systems due to the
reduced maximum ARC size.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Kash Pande <kash@tripleback.net>
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Closes #5845

tests/zfs-tests/tests/functional/zvol/zvol.cfg

@@ -33,6 +33,7 @@ export DISK=${DISKS%% *}
 export TESTVOL=testvol
 export TESTFILE=testfile
 export TESTSNAP=testsnap
-export VOLSIZE=1g
+export VOLSIZE=256m
+export BLOCKSIZE=4K
 export DATA=0
 export ENOSPC=28

tests/zfs-tests/tests/functional/zvol/zvol_ENOSPC/setup.ksh

@@ -40,7 +40,7 @@ if is_mpath_device $DISK; then
 	delete_partitions
 fi
 
-default_zvol_setup $DISK $VOLSIZE
+default_zvol_setup $DISK $VOLSIZE $BLOCKSIZE
 
 $ECHO "y" | $NEWFS -v ${ZVOL_RDEVDIR}/$TESTPOOL/$TESTVOL >/dev/null 2>&1
 (( $? != 0 )) && log_fail "Unable to newfs(1M) $TESTPOOL/$TESTVOL"

tests/zfs-tests/tests/functional/zvol/zvol_common.shlib

@@ -36,17 +36,24 @@
 #
 # Where disk_device: is the name of the disk to be used
 #       volume_size: is the size of the volume, e.g. 2G
+#       block_size:  is the block size of the volume
 #
-function default_zvol_setup # disk_device volume_size
+function default_zvol_setup # disk_device volume_size block_size
 {
-        typeset disk=$1
-        typeset size=$2
+	typeset disk=$1
+	typeset size=$2
+	typeset blocksize=$3
 	typeset savedumpdev
 	typeset -i output
+	typeset create_args
 
-        create_pool $TESTPOOL "$disk"
+	create_pool $TESTPOOL "$disk"
 
-        log_must $ZFS create -V $size $TESTPOOL/$TESTVOL
+	if [ -n "$blocksize" ]; then
+		create_args="-b $blocksize"
+	fi
+
+	log_must $ZFS create $create_args -V $size $TESTPOOL/$TESTVOL
 	block_device_wait
 }