iotests.py: Add qemu_nbd_early_pipe()

qemu_nbd_pipe() currently unconditionally reads qemu-nbd's output.  That
is not ideal because qemu-nbd may keep stderr open after the parent
process has exited.

Currently, the only user of qemu_nbd_pipe() is 147, which discards the
whole output if the parent process returned success and only evaluates
it on error.  Therefore, we can replace qemu_nbd_pipe() by
qemu_nbd_early_pipe() that does the same: Discard the output on success,
and return it on error.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190508211820.17851-3-mreitz@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Max Reitz 2019-05-08 23:18:17 +02:00 committed by Eric Blake
parent 637bc5a5d8
commit 6177b58431
2 changed files with 8 additions and 5 deletions

View File

@ -24,7 +24,7 @@ import socket
import stat
import time
import iotests
from iotests import cachemode, imgfmt, qemu_img, qemu_nbd, qemu_nbd_pipe
from iotests import cachemode, imgfmt, qemu_img, qemu_nbd, qemu_nbd_early_pipe
NBD_PORT_START = 32768
NBD_PORT_END = NBD_PORT_START + 1024
@ -93,7 +93,7 @@ class QemuNBD(NBDBlockdevAddBase):
pass
def _try_server_up(self, *args):
status, msg = qemu_nbd_pipe('-f', imgfmt, test_img, *args)
status, msg = qemu_nbd_early_pipe('-f', imgfmt, test_img, *args)
if status == 0:
return True
if 'Address already in use' in msg:

View File

@ -209,9 +209,9 @@ def qemu_nbd(*args):
'''Run qemu-nbd in daemon mode and return the parent's exit code'''
return subprocess.call(qemu_nbd_args + ['--fork'] + list(args))
def qemu_nbd_pipe(*args):
def qemu_nbd_early_pipe(*args):
'''Run qemu-nbd in daemon mode and return both the parent's exit code
and its output'''
and its output in case of an error'''
subp = subprocess.Popen(qemu_nbd_args + ['--fork'] + list(args),
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
@ -221,7 +221,10 @@ def qemu_nbd_pipe(*args):
sys.stderr.write('qemu-nbd received signal %i: %s\n' %
(-exitcode,
' '.join(qemu_nbd_args + ['--fork'] + list(args))))
return exitcode, subp.communicate()[0]
if exitcode == 0:
return exitcode, ''
else:
return exitcode, subp.communicate()[0]
def compare_images(img1, img2, fmt1=imgfmt, fmt2=imgfmt):
'''Return True if two image files are identical'''