add launchpad bug reports without comments

1 files changed, 117 insertions, 0 deletions

diff --git a/results/scraper/launchpad-without-comments/1661758 b/results/scraper/launchpad-without-comments/1661758
new file mode 100644
index 00000000..b6c4ba30
--- /dev/null
+++ b/results/scraper/launchpad-without-comments/1661758
@@ -0,0 +1,117 @@
+qemu-nbd causes data corruption in VDI-format disk images
+
+Hi,
+
+This is a duplicate of #1422307.  I can't figure out a way to re-open
+it--the status of "Fix Released" is changeable only by a project
+maintainer or bug supervisor--so I'm opening a new bug to make sure
+this gets looked at again.
+
+qemu-nbd will sometimes corrupt VDI disk images.  The bug was thought
+to be fixed in commit f0ab6f109630940146cbaf47d0cd99993ddba824, but
+I'm able to reproduce it in both that commit and in the latest commit
+(a951316b8a5c3c63254f20a826afeed940dd4cba).  I just needed to run more
+iterations of the test.  It's possible that it was partially fixed, or
+that the added serialization made it harder to catch this
+non-deterministic bug, but the same symptoms persist: data corruption
+of VDI-format disk images.
+
+This affects at least qemu-nbd.  I haven't tried reproducing the issue
+with qemu proper or qemu-img, but the original bug report suggests
+that the bug in the common VDI backend may corrupt data written by
+those programs.
+
+Please let me know if I can provide any further information or help
+with testing.  Thank you very much for looking into this!
+
+Test procedure
+**************
+
+The procedure used is the one given by Max Reitz (xanclic) in the
+original bug report, comment 3
+(https://bugs.launchpad.net/qemu/+bug/1422307/comments/3), in the
+section "VDI and NBD over /dev/nbd0", but with up to 1000 iterations
+instead of 10:
+
+  $ cd ~/qemu-origfix-f0ab6f1/bin
+  $ dd if=/dev/urandom of=blob.raw bs=1M count=64
+  64+0 records in
+  64+0 records out
+  67108864 bytes (67 MB) copied, 4.36475 s, 15.4 MB/s
+  $ sudo sh -c 'for i in $(seq 0 999); do ./qemu-img create -f vdi test.vdi 64M > /dev/null; ./qemu-nbd -c /dev/nbd0 test.vdi; sleep 1; ./qemu-img convert -n blob.raw /dev/nbd0; ./qemu-img convert /dev/nbd0 test1.raw; sync; echo 1 > /proc/sys/vm/drop_caches; ./qemu-img convert /dev/nbd0 test2.raw; ./qemu-nbd -d /dev/nbd0 > /dev/null; if ! ./qemu-img compare -q test1.raw test2.raw; then md5sum test1.raw test2.raw; echo "$i failed"; break; fi; done; echo "done"'
+27a66c3a8ac2cf06f2c925968ea9e964  test1.raw
+2da9bf169041a7c2bd144c4ab3a29aea  test2.raw
+64 failed
+done
+
+I've run this process a handful of times, and I've seen it take as
+little as 10 iterations and as many as 161 (taking 32 minutes in the
+latter case).  Please be patient.  Putting the images on tmpfs will
+probably help it go faster, and I have successfully reproduced the
+issue on tmpfs in addition to ext4.
+
+Nothing different was needed to reproduce the issue in a directory
+containing a build of the latest commit.  It still takes somewhere
+around 1-200 iterations to find, in my testing.
+
+Build procedure
+***************
+
+  $ git clone git://git.qemu-project.org/qemu.git
+  [omitted]
+  $ git clone qemu qemu-origfix-f0ab6f1
+  Cloning into 'qemu-origfix-f0ab6f1'...
+  done.
+  $ cd qemu-origfix-f0ab6f1
+  $ git checkout f0ab6f109630940146cbaf47d0cd99993ddba824
+  Note: checking out 'f0ab6f109630940146cbaf47d0cd99993ddba824'.
+  
+  You are in 'detached HEAD' state. You can look around, make experimental
+  changes and commit them, and you can discard any commits you make in this
+  state without impacting any branches by performing another checkout.
+  
+  If you want to create a new branch to retain commits you create, you may
+  do so (now or later) by using -b with the checkout command again. Example:
+  
+    git checkout -b new_branch_name
+  
+  HEAD is now at f0ab6f1... block/vdi: Add locking for parallel requests
+  $ mkdir bin
+  $ cd bin
+  $ script -c'time (../configure --enable-debug --target-list=x86_64-softmmu && make -j6; echo "result: $?")'
+  Script started, file is typescript
+  [omitted; the build typescript is attached separately]
+    LINK  x86_64-softmmu/qemu-system-x86_64
+  result: 0
+  
+  real    1m5.733s
+  user    2m3.904s
+  sys     0m13.828s
+  Script done, file is typescript
+
+Nothing different was done when building the latest commit (besides
+cloning to a different directory, and not running `git checkout`).
+
+Environment
+***********
+
+  * Machine: x86_64
+  
+  * Hypervisor: Xen 4.4 (Debian package xen-hypervisor-4.4-amd64,
+    version 4.4.1-9+deb8u8)
+  
+  * A Xen domU (guest) for building QEMU and reproducing the issue.
+    All testing was done within the virtual machine for convenience
+    and access to better hardware than what I have for my development
+    machine (I expected the build to take much longer than it really
+    does).
+  
+      - x86_64 architecture with six VCPUs and 1.2 GiB RAM allocated,
+        operating in HVM (fully virtualized) mode.
+      
+      - Distribution: Debian 8.7 Jessie amd64
+      
+      - Kernel: Linux 3.16.0 x86_64 (Debian package
+        linux-image-3.16.0-4-amd64, version 3.16.39-1)
+      
+      - Compiler: GCC 4.9.2 (Debian package gcc-4.9, version 4.9.2-10)
\ No newline at end of file