[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



--- Comment #3 from Pranith Kumar K <pkarampu at redhat.com> ---
(In reply to Raghavendra G from comment #2)
> (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.

Just a word of caution, that it is important to do it in backward compatible
way.

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