Matt McCutchen wrote: > Second, it is impossible to make xattr-based checksum caching > foolproof against same-second modification. Suppose a file is written > during second 5 and then rsync caches its checksum during second 8; > now the file has mtime 5 and ctime 8. Sometime later, rsync notices > that the file still has mtime 5 and ctime 8. Does rsync trust the > cached checksum? It must; otherwise the benefit of caching checksums > would be lost. However, rsync will be fooled if the file was modified > and then touched back to mtime 5 during second 8, right after the > checksum was cached. This concern may not be relevant when the > content is slowly changing.
There really ought to be a special kind of xattr which automatically disappears when the file is modified, for this sort of thing. Or a modification serial number, perhaps only incremented when somebody actually has read it. Alas, I think attempts to get one into Linux didn't get very far; nobody thought it was that important. -- Jamie -- To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/rsync Before posting, read: http://www.catb.org/~esr/faqs/smart-questions.html