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Date: Thu, 28 Dec 2006 15:07:43 -0500 From: "Halevy, Benny" <bhalevy@...asas.com> To: "Mikulas Patocka" <mikulas@...ax.karlin.mff.cuni.cz> Cc: "Jeff Layton" <jlayton@...chiereds.net>, "Arjan van de Ven" <arjan@...radead.org>, "Jan Harkes" <jaharkes@...cmu.edu>, "Miklos Szeredi" <miklos@...redi.hu>, <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>, <nfsv4@...f.org> Subject: RE: Finding hardlinks Mikulas Patocka wrote: > >>> This sounds like a bug to me. It seems like we should have a one to one >>> correspondence of filehandle -> inode. In what situations would this not be the >>> case? >> >> Well, the NFS protocol allows that [see rfc1813, p. 21: "If two file handles from >> the same server are equal, they must refer to the same file, but if they are not >> equal, no conclusions can be drawn."] >> >> As an example, some file systems encode hint information into the filehandle >> and the hints may change over time, another example is encoding parent >> information into the filehandle and then handles representing hard links >> to the same file from different directories will differ. > >BTW. how does (or how should?) NFS client deal with cache coherency if >filehandles for the same file differ? > Trond can probably answer this better than me... As I read it, currently the nfs client matches both the fileid and the filehandle (in nfs_find_actor). This means that different filehandles for the same file would result in different inodes :(. Strictly following the nfs protocol, comparing only the fileid should be enough IF fileids are indeed unique within the filesystem. Comparing the filehandle works as a workaround when the exported filesystem (or the nfs server) violates that. From a user stand point I think that this should be configurable, probably per mount point. >Mikulas > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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