049469e7e7
It's entirely surprising that mdnblocks() has the side effect of creating new files on disk, so let's make it not do that. One consequence of the old behavior is that, if running on a damaged cluster that is missing a file, mdnblocks() can recreate the file and allow a subsequent _mdfd_getseg() for a higher segment to succeed. This happens because, while mdnblocks() stops when it finds a segment that is shorter than 1GB, _mdfd_getseg() has no such check, and thus the empty file created by mdnblocks() can allow it to continue its traversal and find higher-numbered segments which remain. It might be a good idea for _mdfd_getseg() to actually verify that each segment it finds is exactly 1GB before proceeding to the next one, but that would involve some additional system calls, so for now I'm just doing this much. Patch by me, per off-list analysis by Kevin Grittner and Rahila Syed. Review by Andres Freund. |
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