Arghh. Found a lack of forethought in the upspin client library.

[David Presotto]

Rodrigo was having problems with upspinfs.  I couldn't duplicate but got logs from him.  I tracked it down to upspinfs getting out of sync with the sequence number of a directory entry.

After drilling down, I found that  it was the cause of a Setattr request to change the mtime.  I use the upspin/client library because it's too hard to not.  However one function, SetTime, doesn't return the updated DirEntry after it does a Dir.Put.  Upspinfs needs that DIrEntry to update its knowledge of the sequence number for subsequent Puts.

I believe my only solution is to add a SetTimeSequenced that takes a sequence numner and returns a DirEntry just as I added a PutSequenced for the same problem with Put.

Anyone care to convince me otherwise?

[Eric Grosse]

Agreed, that's the right fix if you're worried about TOCTOU race for doing Lookup after SetTime. I'm around and will respond promptly to the CL.

[Özgür Kesim]

Hi David,

SetTimeSequenced sounds like the right way to enforce idempotency.

-oec

Thus spake David Presotto (pres...@gmail.com):

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