On Sun, May 03, 2009 at 04:08:59PM +0300, Boaz Harrosh wrote: > On 05/03/2009 09:15 AM, Joel Becker wrote: > > int reflink(const char *oldpath, const char *newpath); > > > > The reflink(2) system call creates reference-counted links. It creates > > a new file that shares the data extents of the source file in a > > copy-on-write fashion. Its calling semantics are identical to link(2). > > Once complete, programs see the new file as a completely separate entry. > > > > Please forgive my complete Unix jargon novice-ness, but from here it looks like the > name is very wrong, and confusing. > > if I put data to link graph then: > > [data]<--[hard-link (one or more)]<--[soft-link(zero or more)] > > The data is other-wise just there on disk but is un available until > it is linked to a dir-entry, at-least one. The middle hard-link is reference > counted and once all uses are removed data can be garbage collected. Soft links > don't follow on-disk data but follow a dir-entry. So if we have a completely > different on disk data we're still in agreement with the dir-entry. A reflink creates a dir entry. That's what newpath is about. Using your graph: [data]<--[reflink (zero or more)]<--[hard-link (one or more)]<--[soft-link(zero or more)] > As my first impression when I read the title of the patch, an English reflink > I would imagine is something more to the left of above graph, between hard-link > and soft-link, something like: link to an invisible dir-entry that is gone once > all soft-links to it are gone. There is no "invisible dir entry". The target is a new file with a new dir entry. It just shares the data extents of the source. Perhaps I can clarify that better. Joel -- "Maybe the time has drawn the faces I recall. But things in this life change very slowly, If they ever change at all." Joel Becker Principal Software Developer Oracle E-mail: joel.becker@xxxxxxxxxx Phone: (650) 506-8127 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
