[Bugs] [Bug 1378550] Moving multiple temporary files to the same destination concurrently causes ESTALE error

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1378550

Raghavendra G <rgowdapp at redhat.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|bugs at gluster.org            |khiremat at redhat.com



--- Comment #2 from Raghavendra G <rgowdapp at redhat.com> ---
(In reply to Pranith Kumar K from comment #1)
> Du, Nitya,
>        Based on my debugging inodelk keeps failing with ESTALE. When I
> checked dht_rename(), I see that the inodelk is done both on source and
> destination inodes. But because the test above can lead to deletion of the
> file we are trying to lock on by the other 'while ()...' process the inodelk
> fails with ESTALE. When I changed the test to rename to independent
> filenames, then everything works as expected.
> On mount1:
> while true; do uuid="`uuidgen`"; echo "some data" > "test$uuid"; mv
> "test$uuid" "test" -f; done
> 
> On mount2:
> while true; do uuid="`uuidgen`"; echo "some data" > "test$uuid"; mv
> "test$uuid" "test2" -f; done
> 
> Not sure how to fix this in DHT though. For now re-assigning the bug to DHT.

locking in dht_rename has two purposes:
1. serialize and ensure atomicity (of each rename) when two parallel renames
are done on the same file.
2. serialize a rename with file migration during rebalance.

The current use-case falls into category 1. I think using entrylk instead of
inodelk solves the problem. However need to think more about this.

Assigning bug to Kotresh as he is working on synchronization issues.

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