[Bugs] [Bug 1352482] New: qemu libgfapi clients hang when doing I/O with 3.7.12

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1352482

            Bug ID: 1352482
           Summary: qemu libgfapi clients hang when doing I/O with 3.7.12
           Product: GlusterFS
           Version: 3.7.12
         Component: libgfapi
          Keywords: Triaged
          Assignee: bugs at gluster.org
          Reporter: kaushal at redhat.com
        QA Contact: sdharane at redhat.com
                CC: bugs at gluster.org
            Blocks: 1350804 (glusterfs-3.7.13)



qemu and related tools (qemu-img) hang when using libgfapi from
glusterfs-3.7.12.

For eg., running the following qemu-img command against a single brick
glusterfs-3.7.12 volume, causes the qemu-img command to hang,

# qemu-img create -f qcow2 gluster://localhost/testvol/testimg.qcow2 10G

With qemu-img at least the hangs happen when creating qcow2 images. The command
doesn't hang when creating raw images.

When creating a qcow2 image, the qemu-img appears to be reloading the glusterfs
graph several times. This can be observed in the attached log where qemu-img is
run against glusterfs-3.7.11.

With glusterfs-3.7.12, this doesn't happen as an early writev failure happens
on the brick transport with a EFAULT (Bad address) errno (see attached log). No
further actions happen after this, and the qemu-img command hangs till the RPC
ping-timeout happens and then fails.

Investigation is still on to find out the cause for this error.

This issue was originally reported in the gluster-users mailing list by Lindsay
Mathieson, Kevin Lemonnier and Dmitry Melekhov. [1][2][3]

[1] https://www.gluster.org/pipermail/gluster-users/2016-June/027144.html
[2] https://www.gluster.org/pipermail/gluster-users/2016-June/027186.html
[3] https://www.gluster.org/pipermail/gluster-users/2016-July/027218.html


Referenced Bugs:

https://bugzilla.redhat.com/show_bug.cgi?id=1350804
[Bug 1350804] Tracker bug for GlusterFS-v3.7.13
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