[Bugs] [Bug 1247108] New: sharding - OS installation on vm image hangs on a sharded volume

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1247108

            Bug ID: 1247108
           Summary: sharding - OS installation on vm image hangs on a
                    sharded volume
           Product: GlusterFS
           Version: mainline
         Component: sharding
          Keywords: Triaged
          Assignee: kdhananj at redhat.com
          Reporter: kdhananj at redhat.com
        QA Contact: bugs at gluster.org
                CC: bugs at gluster.org



Description of problem:
OS installation on a vm image in a sharded volume hangs at some point.

Statedump on the fuse client taken at several points reveals that readv() fop
is hung:

<statedump>
...
...

[global.callpool.stack.1.frame.10]
frame=0x7f0b0bcfd150
ref_count=0
translator=dis-rep-shard
complete=0                  <==== complete is 0.
parent=dis-rep-trace
wind_from=trace_readv
wind_to=FIRST_CHILD(this)->fops->readv
unwind_to=trace_readv_cbk

...
...

[global.callpool.stack.1.frame.14]
frame=0x7f0b0bcd6f40
ref_count=1
translator=dis-rep
complete=0                <======== complete is 0
parent=fuse
wind_from=fuse_readv_resume
wind_to=FIRST_CHILD(this)->fops->readv
unwind_to=fuse_readv_cbk
...
...
</statedump>

This was found to be due to call_count being reduced to -1 at the end of
shard_common_lookup_shards() because of which this particular stack never gets
unwound till FUSE:

(gdb) p (call_frame_t *)0x7f0b0bcfd150
$1 = (call_frame_t *) 0x7f0b0bcfd150
(gdb) p (shard_local_t *)$1->local
$2 = (shard_local_t *) 0x7f0b0086310c
(gdb) p $2->call_count
$3 = -1
(gdb) p $2->eexist_count 
$4 = 1


Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
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Actual results:


Expected results:


Additional info:

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