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Runtime filesystem consistency checkingRuntime filesystem consistency checkingPosted Apr 4, 2012 13:07 UTC (Wed) by ashvin (guest, #83894)In reply to: Runtime filesystem consistency checking by nybble41 Parent article: Runtime filesystem consistency checking
We do handle "unallocated" writes due to shadow paging (e.g., copy-on-write on btrfs) where metadata is written to unallocated regions and then linked to the file-system on commit. We find this linkage at commit point and will not report an error. We haven't worked with online resizing but I suspect the handling should be similar on commit. Writing to unallocated data to which there is no linkage at commit seems suspect: how would the file system know that data is useful in anyway after a crash?
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Runtime filesystem consistency checking Posted Apr 4, 2012 15:30 UTC (Wed) by nybble41 (subscriber, #55106) [Link]
> Writing to unallocated data to which there is no linkage at commit seems suspect: how would the file system know that data is useful in anyway after a crash?
The data would not be useful after a crash; up to the point where the allocation is recorded on disk, there are no references to it, and it can simply revert to unallocated space, canceling the incomplete "transaction".
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