Re: [Qemu-devel] [PATCH v3] qemu-img: Fix overwriting 'ret' before using

[Fam Zheng <famz@redhat.com>]

On 2013年11月13日 20:43, Kevin Wolf wrote:
> From: Fam Zheng <famz@redhat.com>
>
> 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>
> ---
>
> There was another case of overwritten ret that I added in v3.
>
>   qemu-img.c                 |  6 +++---
>   tests/qemu-iotests/048     | 34 ++++++++++++++++++++++++++++++++++
>   tests/qemu-iotests/048.out | 27 ++++++++++++++++++++++++++-
>   3 files changed, 63 insertions(+), 4 deletions(-)
>
> diff --git a/qemu-img.c b/qemu-img.c
> index bf3fb4f..b6b5644 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 9b9d118..9def7fc 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

I think the patterns are incremented for each step, so there's some clue 
of the culprit, if this test fails. But it's up to you. Thanks for 
adding this.

Reviewed-by: Fam Zheng <famz@redhat.com>

> +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 68f65d5..d141e05 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
>