On Mon, 2010-05-24 at 17:47 +0100, Al Viro wrote: > On Mon, May 24, 2010 at 12:21:22PM -0400, Trond Myklebust wrote: > > > Can an nfs4 server e.g. have /x/y being a symlink that resolves to /a/b and > > > allow mounting of both /x/y/c and /a/b/c? Which path would it return to > > > client that has mounted both, walked to some referral point and called > > > nfs_do_refmount(), triggering nfs4_proc_fs_locations()? > > > > > > Trond, Neil? > > > > When mounting /x/y/c in your example above, the NFSv4 protocol requires > > the client itself to resolve the symlink, and then walk down /a/b/c > > (looking up component by component), so it will in practice not see > > anything other than /a/b/c. > > > > If it walks down to a referral, and then calls nfs_do_refmount, it will > > do the same thing: obtain a path /e/f/g on the new server, and then walk > > down that component by component while resolving any symlinks and/or > > referrals that it crosses in the process. > > Ho-hum... What happens if the same fs is mounted twice on server? I.e. > have ext2 from /dev/sda1 mounted on /a and /b on server, then on the client > do mount -t nfs foo:/a /tmp/a; mount -t nfs foo:/b /tmp/b. Which path > would we get from GETATTR with fs_locations requested, if we do it for > /tmp/a/x and /tmp/b/x resp.? Dentry will be the same, since fsid would > match. > > Or would the server refuse to export things that way? I believe that the answer is that most filehandle types include an encoding of the inode number of the export directory. In other words, as long as '/a' and '/b' are different directories, then they will result in the generation of different filehandles for /a/x and /b/x. It seems that is not always the case, though. According to the definition of mk_fsid(), it looks as if the 'FSID_UUID8' and 'FSID_UUID16' filehandle types only encode the uuid of the filesystem, and have no inode information. They will therefore not be able to distinguish between an export through '/a' or '/b'. Neil, Bruce am I right? Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
