[PULL 03/12] qemu-img: Flush stdout before before potential stderr messages

[Kevin Wolf]

From: Eric Blake <eblake@redhat.com>

During 'qemu-img create ... 2>&1', if --quiet is not in force, we can
end up with buffered I/O in stdout that was produced before failure,
but which appears in output after failure.  This is confusing; the fix
is to flush stdout prior to attempting anything that might produce an
error message.  Several iotests demonstrate the resulting ordering
change now that the merged outputs now reflect chronology.  (An even
better fix would be to avoid printf from within block.c altogether,
but that's much more invasive...)

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200706203954.341758-2-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c                    | 1 +
 tests/qemu-iotests/049.out | 8 ++++----
 tests/qemu-iotests/054.out | 2 +-
 tests/qemu-iotests/079.out | 2 +-
 tests/qemu-iotests/112.out | 4 ++--
 tests/qemu-iotests/259.out | 2 +-
 6 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/block.c b/block.c
index 6dbcb7e083..a568196ba2 100644
--- a/block.c
+++ b/block.c
@@ -6186,6 +6186,7 @@ void bdrv_img_create(const char *filename, const char 
*fmt,
         printf("Formatting '%s', fmt=%s ", filename, fmt);
         qemu_opts_print(opts, " ");
         puts("");
+        fflush(stdout);
     }
 
     ret = bdrv_create(drv, filename, opts, &local_err);
diff --git a/tests/qemu-iotests/049.out b/tests/qemu-iotests/049.out
index c54ae21b86..22f395246b 100644
--- a/tests/qemu-iotests/049.out
+++ b/tests/qemu-iotests/049.out
@@ -167,12 +167,12 @@ qemu-img create -f qcow2 -o compat=1.1 TEST_DIR/t.qcow2 
64M
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 compat=1.1 
cluster_size=65536 lazy_refcounts=off refcount_bits=16 compression_type=zlib
 
 qemu-img create -f qcow2 -o compat=0.42 TEST_DIR/t.qcow2 64M
-qemu-img: TEST_DIR/t.qcow2: Invalid parameter '0.42'
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 compat=0.42 
cluster_size=65536 lazy_refcounts=off refcount_bits=16 compression_type=zlib
+qemu-img: TEST_DIR/t.qcow2: Invalid parameter '0.42'
 
 qemu-img create -f qcow2 -o compat=foobar TEST_DIR/t.qcow2 64M
-qemu-img: TEST_DIR/t.qcow2: Invalid parameter 'foobar'
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 compat=foobar 
cluster_size=65536 lazy_refcounts=off refcount_bits=16 compression_type=zlib
+qemu-img: TEST_DIR/t.qcow2: Invalid parameter 'foobar'
 
 == Check preallocation option ==
 
@@ -183,8 +183,8 @@ qemu-img create -f qcow2 -o preallocation=metadata 
TEST_DIR/t.qcow2 64M
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 cluster_size=65536 
preallocation=metadata lazy_refcounts=off refcount_bits=16 compression_type=zlib
 
 qemu-img create -f qcow2 -o preallocation=1234 TEST_DIR/t.qcow2 64M
-qemu-img: TEST_DIR/t.qcow2: Invalid parameter '1234'
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 cluster_size=65536 
preallocation=1234 lazy_refcounts=off refcount_bits=16 compression_type=zlib
+qemu-img: TEST_DIR/t.qcow2: Invalid parameter '1234'
 
 == Check encryption option ==
 
@@ -206,7 +206,7 @@ qemu-img create -f qcow2 -o compat=0.10,lazy_refcounts=off 
TEST_DIR/t.qcow2 64M
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 compat=0.10 
cluster_size=65536 lazy_refcounts=off refcount_bits=16 compression_type=zlib
 
 qemu-img create -f qcow2 -o compat=0.10,lazy_refcounts=on TEST_DIR/t.qcow2 64M
-qemu-img: TEST_DIR/t.qcow2: Lazy refcounts only supported with compatibility 
level 1.1 and above (use version=v3 or greater)
 Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=67108864 compat=0.10 
cluster_size=65536 lazy_refcounts=on refcount_bits=16 compression_type=zlib
+qemu-img: TEST_DIR/t.qcow2: Lazy refcounts only supported with compatibility 
level 1.1 and above (use version=v3 or greater)
 
 *** done
diff --git a/tests/qemu-iotests/054.out b/tests/qemu-iotests/054.out
index e6ec430edd..71f18bb987 100644
--- a/tests/qemu-iotests/054.out
+++ b/tests/qemu-iotests/054.out
@@ -1,8 +1,8 @@
 QA output created by 054
 
 creating too large image (1 EB)
-qemu-img: TEST_DIR/t.IMGFMT: The image size is too large for file format 
'IMGFMT' (try using a larger cluster size)
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1152921504606846976
+qemu-img: TEST_DIR/t.IMGFMT: The image size is too large for file format 
'IMGFMT' (try using a larger cluster size)
 
 creating too large image (1 EB) using qcow2.py
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296
diff --git a/tests/qemu-iotests/079.out b/tests/qemu-iotests/079.out
index aab922fb36..f65a9ca84f 100644
--- a/tests/qemu-iotests/079.out
+++ b/tests/qemu-iotests/079.out
@@ -9,6 +9,6 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 
preallocation=metadat
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 
preallocation=metadata
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 
preallocation=metadata
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 
preallocation=metadata
-qemu-img: TEST_DIR/t.IMGFMT: Cluster size must be a power of two between 512 
and 2048k
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 
preallocation=metadata
+qemu-img: TEST_DIR/t.IMGFMT: Cluster size must be a power of two between 512 
and 2048k
 *** done
diff --git a/tests/qemu-iotests/112.out b/tests/qemu-iotests/112.out
index ae0318cabe..5e77e38a7a 100644
--- a/tests/qemu-iotests/112.out
+++ b/tests/qemu-iotests/112.out
@@ -2,7 +2,6 @@ QA output created by 112
 
 === refcount_bits limits ===
 
-qemu-img: TEST_DIR/t.IMGFMT: Refcount width must be a power of two and may not 
exceed 64 bits
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 qemu-img: TEST_DIR/t.IMGFMT: Refcount width must be a power of two and may not 
exceed 64 bits
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 refcount_bits=-1
@@ -10,6 +9,7 @@ qemu-img: TEST_DIR/t.IMGFMT: Refcount width must be a power of 
two and may not e
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 qemu-img: TEST_DIR/t.IMGFMT: Refcount width must be a power of two and may not 
exceed 64 bits
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+qemu-img: TEST_DIR/t.IMGFMT: Refcount width must be a power of two and may not 
exceed 64 bits
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 refcount bits: 1
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
@@ -21,10 +21,10 @@ refcount bits: 16
 
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 refcount bits: 16
-qemu-img: TEST_DIR/t.IMGFMT: Different refcount widths than 16 bits require 
compatibility level 1.1 or above (use version=v3 or greater)
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
 qemu-img: TEST_DIR/t.IMGFMT: Different refcount widths than 16 bits require 
compatibility level 1.1 or above (use version=v3 or greater)
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864
+qemu-img: TEST_DIR/t.IMGFMT: Different refcount widths than 16 bits require 
compatibility level 1.1 or above (use version=v3 or greater)
 
 === Snapshot limit on refcount_bits=1 ===
 
diff --git a/tests/qemu-iotests/259.out b/tests/qemu-iotests/259.out
index ffed19c2a0..e27b9ff38d 100644
--- a/tests/qemu-iotests/259.out
+++ b/tests/qemu-iotests/259.out
@@ -9,6 +9,6 @@ virtual size: 64 MiB (67108864 bytes)
 disk size: unavailable
 
 --- Testing creation for which the node would need to grow ---
-qemu-img: TEST_DIR/t.IMGFMT: Could not resize image: Image format driver does 
not support resize
 Formatting 'TEST_DIR/t.IMGFMT', fmt=qcow2 size=67108864 preallocation=metadata
+qemu-img: TEST_DIR/t.IMGFMT: Could not resize image: Image format driver does 
not support resize
 *** done
-- 
2.25.4