[Qemu-devel] [PATCH v3] iotests: Filter 175's allocation information

[Max Reitz <mreitz@redhat.com>]

It is possible for an empty file to take up blocks on a filesystem, for
example:

$ qemu-img create -f raw test.img 1G
Formatting 'test.img', fmt=raw size=1073741824
$ mkfs.ext4 -I 128 -q test.img
$ mkdir test-mount
$ sudo mount -o loop test.img test-mount
$ sudo touch test-mount/test-file
$ stat -c 'blocks=%b' test-mount/test-file
blocks=8

These extra blocks (one cluster) are apparently used for metadata,
because they are always there, on top of blocks used for data:

$ sudo dd if=/dev/zero of=test-mount/test-file bs=1M count=1
1+0 records in
1+0 records out
1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.00135339 s, 775 MB/s
$ stat -c 'blocks=%b' test-mount/test-file
blocks=2056

Make iotest 175 take this into account.

Reported-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Nir Soffer <nsoffer@redhat.com>
---
v3:
- Actually tested this on an FS with the behavior in question and
  noticed the patterns were lacking a $.  Since I'm now sending a v3
  anyway, I might as well fix it with the heavy hammer and make it a
  ($|[^0-9]).
- Added example configuration to the commit message [Nir]
- Kept the R-bs because I didn't feel too bad about doing so.
---
 tests/qemu-iotests/175     | 26 ++++++++++++++++++++++----
 tests/qemu-iotests/175.out |  8 ++++----
 2 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/tests/qemu-iotests/175 b/tests/qemu-iotests/175
index d0ffc495c2..51e62c8276 100755
--- a/tests/qemu-iotests/175
+++ b/tests/qemu-iotests/175
@@ -28,10 +28,25 @@ status=1	# failure is the default!
 
 _cleanup()
 {
-	_cleanup_test_img
+    _cleanup_test_img
+    rm -f "$TEST_DIR/empty"
 }
 trap "_cleanup; exit \$status" 0 1 2 3 15
 
+# Some file systems sometimes allocate extra blocks independently of
+# the file size.  This function hides the resulting difference in the
+# stat -c '%b' output.
+# Parameter 1: Number of blocks an empty file occupies
+# Parameter 2: Image size in bytes
+_filter_blocks()
+{
+    extra_blocks=$1
+    img_size=$2
+
+    sed -e "s/blocks=$extra_blocks\\(\$\\|[^0-9]\\)/nothing allocated/" \
+        -e "s/blocks=$((extra_blocks + img_size / 512))\\(\$\\|[^0-9]\\)/everything allocated/"
+}
+
 # get standard environment, filters and checks
 . ./common.rc
 . ./common.filter
@@ -40,18 +55,21 @@ _supported_fmt raw
 _supported_proto file
 _supported_os Linux
 
-size=1m
+size=$((1 * 1024 * 1024))
+
+touch "$TEST_DIR/empty"
+extra_blocks=$(stat -c '%b' "$TEST_DIR/empty")
 
 echo
 echo "== creating image with default preallocation =="
 _make_test_img $size | _filter_imgfmt
-stat -c "size=%s, blocks=%b" $TEST_IMG
+stat -c "size=%s, blocks=%b" $TEST_IMG | _filter_blocks $extra_blocks $size
 
 for mode in off full falloc; do
     echo
     echo "== creating image with preallocation $mode =="
     IMGOPTS=preallocation=$mode _make_test_img $size | _filter_imgfmt
-    stat -c "size=%s, blocks=%b" $TEST_IMG
+    stat -c "size=%s, blocks=%b" $TEST_IMG | _filter_blocks $extra_blocks $size
 done
 
 # success, all done
diff --git a/tests/qemu-iotests/175.out b/tests/qemu-iotests/175.out
index 76c02c6a57..6d9a5ed84e 100644
--- a/tests/qemu-iotests/175.out
+++ b/tests/qemu-iotests/175.out
@@ -2,17 +2,17 @@ QA output created by 175
 
 == creating image with default preallocation ==
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576
-size=1048576, blocks=0
+size=1048576, nothing allocated
 
 == creating image with preallocation off ==
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 preallocation=off
-size=1048576, blocks=0
+size=1048576, nothing allocated
 
 == creating image with preallocation full ==
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 preallocation=full
-size=1048576, blocks=2048
+size=1048576, everything allocated
 
 == creating image with preallocation falloc ==
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 preallocation=falloc
-size=1048576, blocks=2048
+size=1048576, everything allocated
  *** done
-- 
2.21.0