Commit fa952fcd authored Nov 06, 2017 by Jim Harris

test/nbd: use dd to confirm I/O path is ready



We see a delay, especially in VMs, between when the
block layer reports the nbd device as ready (with
non-zero size) and when I/O will complete successfully
without an -ENOSPC error.

So to compensate, dd the first block of the nbd
device to a temporary file, then check the size of that
file to confirm the nbd device is ready for I/O.
Note that dd with a zero-sized input file will always
complete successfully just with 0 blocks transferred.
So we cannot rely on the return value of dd - we check
the size of the written file instead.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: I84ea3b663668a27021619cbee502769af4922937

Reviewed-on: https://review.gerrithub.io/385936


Reviewed-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>

parent 2f228848

scripts/autotest_common.sh

+16 −0

Original line number	Diff line number	Diff line
		@@ -207,6 +207,22 @@ function waitfornbd() {

		for ((i=1; i<=20; i++)); do
		if grep -q -w $nbd_name /proc/partitions; then
		break
		else
		sleep 0.1
		fi
		done

		# The nbd device is now recognized as a block device, but there can be
		# a small delay before we can start I/O to that block device. So loop
		# here trying to read the first block of the nbd block device to a temp
		# file. Note that dd returns success when reading an empty file, so we
		# need to check the size of the output file instead.
		for ((i=1; i<=20; i++)); do
		dd if=/dev/$nbd_name of=/tmp/nbdtest bs=4096 count=1 iflag=direct
		size=`stat -c %s /tmp/nbdtest`
		rm -f /tmp/nbdtest
		if [ "$size" != "0" ]; then
		return 0
		else
		sleep 0.1