On Thu, Apr 03, 2014 at 02:55:04PM -0400, Jeff Layton wrote: > On Thu, 03 Apr 2014 13:51:06 -0400 > Mark Lord <mlord@xxxxxxxxx> wrote: > > > On 14-04-03 01:16 PM, J. Bruce Fields wrote: > > > On Thu, Apr 03, 2014 at 12:33:55PM -0400, Mark Lord wrote: > > >> This commit from linux-3.14 breaks our NFS-root clients here: > > >> > > >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=6e14b46b91fee8a049b0940333ce13a820beaaa5 > > >> > > >> > > >> - *p++ = htonl((u32) stat->mode); > > >> + *p++ = htonl((u32) (stat->mode & S_IALLUGO)); > > >> > > >> > > >> Reverting the one-liner above (on the server) fixes it for us, > > >> as does reverting back to linux-3.13.8 on the server. > > >> > > >> The NFS-root clients are on PowerPC (big-endian) architecture, > > >> running linux-3.12.16. The NFS server is on an Intel PC running linux-3.14. > > >> > > >> ACL is completely disabled on server and client, > > >> and we're using NFSv2/v3. No support for v4. > > >> > > >> I instrumented the function to see what other bits were being cleared > > >> by the (stat->mode & S_IALLUGO) masking. The results are attached. > > > > > > Hm, it sounds like a bug in the client if it's depending on those high > > > bits. > > > > But only for mounting / starting up from the nfsroot, it seems. > > I wonder if there's an unusual code path for that in there? > > The regular stuff looks mostly fine: > > > > p = xdr_decode_ftype3(p, &fmode); > > fattr->mode = (be32_to_cpup(p++) & ~S_IFMT) | fmode; > > > > Except perhaps that second line ought to use the same mask > > as the server side is using, just in case there are some other > > stray high (higher than S_IFMT) bits in there now/someday. > > > > > The original behavior was in practice harmless and changing it broke > > > something, so I think we should definitely just revert this patch. > > > > Yup. Who? > > > > > But the client may need fixing too. > > > > Probably a good thing in the longer term, for better compatibility > > with non-Linux servers. But we'll still have to keep the revert > > on the server (nfsd) code for backward compatibility, I think. > > > > Cheers > > > > It would be good to understand where this is broken in the client. > > It's incorrect for the client to interpret those bits, as I think that > there's no guarantee that other OS's implement the type bits in the > same way that Linux does. So if you end up mounting a different OS, > it's possible that the client will get that wrong... It turns out these bits actually are defined in rfc 1094, so this is just an odd NFSv2-specific wart, and the nfsd change was just flat-out wrong. --b. -- 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
