Qu Wenruo posted on Tue, 12 Jan 2016 12:51:33 +0800 as excerpted: > Duncan wrote on 2016/01/12 04:13 +0000: >> Qu Wenruo posted on Tue, 12 Jan 2016 11:09:23 +0800 as excerpted: >> >>> Now we hope to add support to enable/disable dedup per-file. >>> Much like current NODATACOW/NOCOMPRESS for inode. >> >> How is this going to work? >> >> NODATACOW/NOCOMPRESS can apply to a single file. But a dup flag, by >> definition, needs two files, except for the special case of parts of a >> file duplicating other parts of the same file. > > You are still thinking in the way off-band dedup. > So the things should be quite easy to understand: > > For normal case (no NODEDUP flag), valid data(page cache) will be hashed > to find if it's a duplicated one. > > For NODEDUP flag case, all its page cache just direct write to disk or > compressed then write to disk. > No hash will be calculated. Oh, _NO_DEDUP. =:^) Opposite the dedup logic implied by the subject, with no hint in the original post indicating logic actually the reverse of that. NODEDUP indeed makes more sense, since with a mount or filesystem option enabling dedup, it would then be the default and nodedup as a per-file exception is the next logical extension. Thanks. I knew I must be missing something. A little negation makes a big difference! =:^) -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
