[pnfs] 19 questions

[Dean Hildebrand]

William A. (Andy) Adamson wrote:
>
>
> On 2/4/08, *Dean Hildebrand* <seattleplus at gmail.com 
> <mailto:seattleplus at gmail.com>> wrote:
>
>     Some questions about draft 19 (not 19 questions):
>
>     1) On the server I need the superblock so I can call the getdeviceinfo
>     export operation.  
>
>
> why? the deviceid space is global.
Well, the devices and the device ids still come from the file system, 
and the only way I know how to talk to the file system is through the 
export ops, which requires a superblock. 

To make them globally unique, through coincidence or the fact that we 
are all very like minded people, we had already coded up the deviceid on 
the server as Benny suggested:

struct pnfs_deviceid {
	u64	ex_fsid;
	__be64	devid;
};

One limitation here is that in include/linux/nfsd/nfsfh.h it defines the 
sizes for various types of fsids:
static inline int key_len(int type)
{
        switch(type) {
        case FSID_DEV:          return 8;
        case FSID_NUM:          return 4;
        case FSID_MAJOR_MINOR:  return 12;
        case FSID_ENCODE_DEV:   return 8;
        case FSID_UUID4_INUM:   return 8;
        case FSID_UUID8:        return 8;
        case FSID_UUID16:       return 16;
        case FSID_UUID16_INUM:  return 24;
        default: return 0;
        }
}

So if we are limiting the fsid to be only 8 bytes, then there are 
several types of fsids we cannot support.  I'm wondering if this is a 
major problem for all OSs or just a hassle for all OSs.  There are 
workarounds I guess (replace fsid with a made up id in /etc/exports) but 
they seem like a hassle.  What do people think?
Dean
>
> -->Andy
>
>     The problem is that getdeviceinfo no longer includes
>     the current_fh.  Is there a way on the server to get the superblock
>     without the filehandle? (maybe using something in the
>     session?)  If not,
>     then we will have to encode something in the device id that allows
>     us to
>     map to the superblock (is the fsid enough?)  Any ideas?
>
>     2) Can getdeviceinfo return a device for the wrong layout type?  It
>     seems that getdeviceinfo returns the layout type, which seems a little
>     silly to me.  If it should return the layout type, and it doesn't
>     match
>     the requesting layout type, what should the client do?
>
>     3) In draft-19, should bitmap4 not have <>?
>     bitmap4<> typedef uint32_t bitmap4<>;
>           ^^^^
>     For reference, in rfc3530 it does not have the <>. (other ops have the
>     <> added as well)
>
>     Thanks,
>     Dean
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>