Messages in this thread | | | Date | Mon, 5 Apr 2004 13:46:37 +0200 | From | Pavel Machek <> | Subject | Re: [PATCH] cowlinks v2 |
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Hi!
> > > get_data_id() is one way to detect equivalent files. Another would be > > > a function files_equal(fd1, fd2) which returns a boolean. > > > > files_equal(...) would lead to quadratic number of calls, no? > > > > > get_data_id() has the advantage that it can report immediately whether > > > a file has _any_ cowlink peers, which is important for programs that > > > scan trees. Perhaps getxattr() would be reasonable interface, using a > > > named attribute "data-id". > > > > Yes, get_data_id() is extremely ugly name. > > I think it is worth asking if we really want to give userspace a way of > doing this or not. It exposes fairly low level FS details to userspace, > and this will limit our ability to change the implementation of the FS > in the future (partially shared files?). Certainly there has been some > pain caused over the years because userspace can ask for the inode number, > and people have written file systems which do not use inodes. Then they > have to kluge around this and make something up. I would hate to see > us implement an interface that causes long term pain.
It should not be painfull, get_data_id() can allways return -Esomething, meaning "I do not know".
> I also cant really think of anyone who would need this information. I have > seen diff and tar used as examples. Perhaps diff would run faster but that > seems like a very special case thing, and diff will certainly work w/o it.
Speeding up diff was one of main cowlinks motivations. Pavel -- Horseback riding is like software... ...vgf orggre jura vgf serr. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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