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Where the the correctness go?Where the the correctness go?Posted Mar 14, 2009 5:16 UTC (Sat) by foom (subscriber, #14868)In reply to: Where the the correctness go? by flewellyn Parent article: Ts'o: Delayed allocation and the zero-length file problem
Open a brand new file, write, close, "atomic" rename on top of an existing file. No O_TRUNC. This
sequence causes the problem.
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Where the the correctness go? Posted Mar 14, 2009 5:33 UTC (Sat) by flewellyn (subscriber, #5047) [Link]
Hmm...in that case, definitely fsync after rename.
Where the the correctness go? Posted Mar 15, 2009 1:43 UTC (Sun) by droundy (subscriber, #4559) [Link]
Sorry, that's wrong. fsync before rename.
Where the the correctness go? Posted Mar 14, 2009 6:21 UTC (Sat) by bojan (subscriber, #14302) [Link]
Please read the manual page for close(). Just because you closed the file doesn't mean your data is on disk.
As for rename, your file gets renamed _atomically_ just fine. However, if you don't _commit_ your writes (make the changes durable, call fsync), the renamed file will have zero size.
This is not a file system problem, but an application problem.
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