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... -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
