qemu-img: Flush stdout before before potential stderr messages

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>

7 files changed, 13 insertions, 12 deletions

diff --git a/block.c b/block.c
index 3031413deb..98cad57cda 100644
--- a/block.c
+++ b/block.c
@@ -6164,6 +6164,7 @@ 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 e77966446b..4c21dc70a5 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 cluster_size=65536 compression_type=zlib size=67108864 compat=1.1 lazy_refcounts=off refcount_bits=16
 
 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 cluster_size=65536 compression_type=zlib size=67108864 compat=0.42 lazy_refcounts=off refcount_bits=16
+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 cluster_size=65536 compression_type=zlib size=67108864 compat=foobar lazy_refcounts=off refcount_bits=16
+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 cluster_size=65536 preallocation=metadata compression_type=zlib size=67108864 lazy_refcounts=off refcount_bits=16
 
 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 cluster_size=65536 preallocation=1234 compression_type=zlib size=67108864 lazy_refcounts=off refcount_bits=16
+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 cluster_size=65536 compression_type=zlib size=67108864 compat=0.10 lazy_refcounts=off refcount_bits=16
 
 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 cluster_size=65536 compression_type=zlib size=67108864 compat=0.10 lazy_refcounts=on refcount_bits=16
+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 182655dbf6..dd3cc4383c 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
@@ -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
diff --git a/tests/qemu-iotests/282.out b/tests/qemu-iotests/282.out
index 5d079dabce..67db7ab15a 100644
--- a/tests/qemu-iotests/282.out
+++ b/tests/qemu-iotests/282.out
@@ -1,11 +1,11 @@
 QA output created by 282
 == Create non-UTF8 secret ==
 == Throws an error because of invalid UTF-8 secret ==
-qemu-img: vol.img: Data from secret sec0 is not valid UTF-8
 Formatting 'vol.img', fmt=luks size=4194304 key-secret=sec0
+qemu-img: vol.img: Data from secret sec0 is not valid UTF-8
 == Image file should not exist after the error ==
 == Create a stub image file and run qemu-img again ==
-qemu-img: vol.img: Data from secret sec0 is not valid UTF-8
 Formatting 'vol.img', fmt=luks size=4194304 key-secret=sec0
+qemu-img: vol.img: Data from secret sec0 is not valid UTF-8
 == Pre-existing image file should also be deleted after the error ==
- *** done
+*** done