Yuen L. Lee wrote:
Thanks for the explanation. I'm curious as to what will be the contents of my file, assuming the system panics right after the metadada of my file is logged to the log_map (on-disk map).
Depends on if the memory pages that hold this data have been flushed to the file system or not, totally irrelevant if the metadata changes have made it to the on disk log or not. If the metadata changes include additional blocks being added to the file, then if you panic BEFORE these changes were written to the ondisk log, your file will not contain these additional blocks, and these blocks will still be marked free after reboot. If you extend your file and the metadata changes get written to the ondisk log, and then you panic, your file will still show that these blocks have been added to your file, these blocks are NOT marked free. But what is the contents of these block? Depends on if the memory pages mapping the blocks had been flushed to disk before the panic or not. Again, totally irrelevant to if the metadata changes have made it to the ondisk log or not. Again, logging only guarentees consistency of metadata changes, not file contents.
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