Re: linux-3.14 nfsd regression

[Mark Lord <mlord@pobox.com>]

On 14-04-03 12:33 PM, 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.
..


Looking into the (previously attached) trace, the bits that seem to be
getting chopped most often are S_IFREG (0x8000) and S_IFDIR (0x4000).
It appears that one/both of those are needed for mounting nfsroot.


[ 2733.823753] encode_fattr: mode=0x000041ed mask=0x00000fff
[ 2733.824217] encode_fattr: mode=0x000041ed mask=0x00000fff
[ 2733.838769] encode_fattr: mode=0x000041ed mask=0x00000fff
[ 2733.839175] encode_fattr: mode=0x0000a1ff mask=0x00000fff
[ 2733.839895] encode_fattr: mode=0x000081ed mask=0x00000fff
[ 2733.840388] encode_fattr: mode=0x000081ed mask=0x00000fff
[ 2733.840431] encode_fattr: mode=0x000081ed mask=0x00000fff
[ 2733.841256] encode_fattr: mode=0x000041ed mask=0x00000fff
[ 2733.841659] encode_fattr: mode=0x0000a1ff mask=0x00000fff
[ 2733.842379] encode_fattr: mode=0x000081ed mask=0x00000fff
[ 2733.842825] encode_fattr: mode=0x000081ed mask=0x00000fff
[ 2733.842879] encode_fattr: mode=0x000081ed mask=0x00000fff
[ 2733.843876] encode_fattr: mode=0x000081ed mask=0x00000fff
[ 2733.843924] encode_fattr: mode=0x000081ed mask=0x00000fff
...