qemu-img: Fix overwriting 'ret' before using

This patch moves ret assignment after reporting original error.

We were lucky to pass qemu-iotests 048 (qemu-img compare case) but when
I tried to run with TEST_DIR=/tmp (tmpfs), it fails with a "wrong"
mismatch offset. This fixes two bugs.

In the first if branch, setting ret to 1 before using it makes dead code
in the next line: pnum is never added to mismatch offset even if ret was
0.

In the other if branch, currently the output error is always -4:
  strerror(-4) -> Unknown error -4

Added regression test in case 048.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Amos Kong <akong@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>

3 files changed, 63 insertions, 4 deletions

diff --git a/qemu-img.c b/qemu-img.c
index bf3fb4f8a6..b6b5644cb6 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1020,10 +1020,10 @@ static int img_compare(int argc, char **argv)
                 }
                 ret = compare_sectors(buf1, buf2, nb_sectors, &pnum);
                 if (ret || pnum != nb_sectors) {
-                    ret = 1;
                     qprintf(quiet, "Content mismatch at offset %" PRId64 "!\n",
                             sectors_to_bytes(
                                 ret ? sector_num : sector_num + pnum));
+                    ret = 1;
                     goto out;
                 }
             }
@@ -1045,9 +1045,9 @@ static int img_compare(int argc, char **argv)
             }
             if (ret) {
                 if (ret < 0) {
-                    ret = 4;
                     error_report("Error while reading offset %" PRId64 ": %s",
                                  sectors_to_bytes(sector_num), strerror(-ret));
+                    ret = 4;
                 }
                 goto out;
             }
@@ -1092,10 +1092,10 @@ static int img_compare(int argc, char **argv)
                                           filename_over, buf1, quiet);
                 if (ret) {
                     if (ret < 0) {
-                        ret = 4;
                         error_report("Error while reading offset %" PRId64
                                      " of %s: %s", sectors_to_bytes(sector_num),
                                      filename_over, strerror(-ret));
+                        ret = 4;
                     }
                     goto out;
                 }
diff --git a/tests/qemu-iotests/048 b/tests/qemu-iotests/048
index 9b9d118ef3..9def7fcc8c 100755
--- a/tests/qemu-iotests/048
+++ b/tests/qemu-iotests/048
@@ -74,5 +74,39 @@ _compare
 io_pattern write 0 $CLUSTER_SIZE 0 1 123
 _compare
 
+# Test unaligned case of mismatch offsets in allocated clusters
+_make_test_img $size
+io_pattern write 0 512 0 1 100
+cp "$TEST_IMG" "$TEST_IMG2"
+io_pattern write 512 512 0 1 101
+_compare
+
+# Test cluster allocated in one, with IO error
+cat > "$TEST_DIR/blkdebug.conf"<<EOF
+[inject-error]
+event = "read_aio"
+errno = "5"
+once ="off"
+EOF
+_make_test_img $size
+cp "$TEST_IMG" "$TEST_IMG2"
+io_pattern write 512 512 0 1 102
+TEST_IMG="blkdebug:$TEST_DIR/blkdebug.conf:$TEST_IMG" _compare 2>&1 |\
+    _filter_testdir | _filter_imgfmt
+
+# Test cluster allocated in one, with different sizes and IO error in the part
+# that exists only in one image
+cat > "$TEST_DIR/blkdebug.conf"<<EOF
+[inject-error]
+event = "read_aio"
+errno = "5"
+once ="off"
+EOF
+_make_test_img $size
+TEST_IMG="$TEST_IMG2" _make_test_img 0
+io_pattern write 512 512 0 1 102
+TEST_IMG="blkdebug:$TEST_DIR/blkdebug.conf:$TEST_IMG" _compare 2>&1 |\
+    _filter_testdir | _filter_imgfmt
+
 # Cleanup
 status=0
diff --git a/tests/qemu-iotests/048.out b/tests/qemu-iotests/048.out
index 68f65d5e19..d141e0579f 100644
--- a/tests/qemu-iotests/048.out
+++ b/tests/qemu-iotests/048.out
@@ -1,5 +1,5 @@
 QA output created by 048
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
 === IO: pattern 45
 qemu-io> wrote 4096/4096 bytes at offset 524288
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
@@ -28,4 +28,29 @@ qemu-io> wrote 4096/4096 bytes at offset 0
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qemu-io> Content mismatch at offset 0!
 1
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
+=== IO: pattern 100
+qemu-io> wrote 512/512 bytes at offset 0
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> === IO: pattern 101
+qemu-io> wrote 512/512 bytes at offset 512
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> Content mismatch at offset 512!
+1
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
+=== IO: pattern 102
+qemu-io> wrote 512/512 bytes at offset 512
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> qemu-img: Error while reading offset 0 of blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
+qemu-img: Error while reading offset 0: Input/output error
+4
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 
+Formatting 'TEST_DIR/t.IMGFMT.2', fmt=IMGFMT size=0 
+=== IO: pattern 102
+qemu-io> wrote 512/512 bytes at offset 512
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+qemu-io> qemu-img: Error while reading offset 0 of blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
+qemu-img: Error while reading offset 0 of blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
+Warning: Image size mismatch!
+4
 Cleanup