dtrace discuss - Apr 2006 - Locating the pathname in nfs3_access()?

Howdy,

I am trying to find the full pathname of the entity being checked in 
nfs3_access(), and have hit a bit of snag. I was hoping to use the 
r_unlname and r_rpath entries in the rnode_t that arg0->v_data points
to, but they appear to be NULL:

$ cat printaddr.d

fbt:nfs:nfs3_access:entry
{
     /* arg0 -> vnode_t */
     /* arg0 -> v_data -> r_path  */
     printf("\nStart: ***********************\n");
     printf("vnode_t: %x\n", arg0);
     printf("vdata_t: %x\n", (uintptr_t)(((vnode_t
*)arg0)->v_data));
     printf("r_path: %x\n", (uintptr_t)(((rnode_t *)(((vnode_t
     *)arg0)->v_data))->r_path));
     printf("r_unlname: %x\n", (uintptr_t)(((rnode_t *)(((vnode_t
     *)arg0)->v_data))->r_unlname));
     printf("End: ***********************\n");
}

$ dtrace -s printaddr.d

   3  36888                nfs3_access:entry
Start: ***********************
vnode_t: cc804300
vdata_t: cd0f5c48
r_path: 0
r_unlname: 0
End: ***********************

I traced down r_rpath to create_rnode, and it looks like it''s only set
if
a failover mount is in use. When I opengrok or r_unldvp, it shows up in 
the NFSv3 inactive, rename and remove routines, and I wasn''t able to
spot
the location where r_unlname originalyl gets set (poor eyes I recon). Does 
anyone happen to know if there is a way to get the full path to the file 
(or directory) being checked in nfs3_access?

Thanks for any insight,
- Ryan
--
UNIX Administrator
http://daemons.net/~matty

On Mon, Matty wrote:
> 
> Howdy,
> 
> I am trying to find the full pathname of the entity being checked in 
> nfs3_access(), and have hit a bit of snag. I was hoping to use the 
> r_unlname and r_rpath entries in the rnode_t that arg0->v_data points
> to, but they appear to be NULL:
> 
> $ cat printaddr.d
> 
> fbt:nfs:nfs3_access:entry
> {
>     /* arg0 -> vnode_t */
>     /* arg0 -> v_data -> r_path  */
>     printf("\nStart: ***********************\n");
>     printf("vnode_t: %x\n", arg0);
>     printf("vdata_t: %x\n", (uintptr_t)(((vnode_t
*)arg0)->v_data));
>     printf("r_path: %x\n", (uintptr_t)(((rnode_t *)(((vnode_t
>     *)arg0)->v_data))->r_path));
>     printf("r_unlname: %x\n", (uintptr_t)(((rnode_t *)(((vnode_t
>     *)arg0)->v_data))->r_unlname));
>     printf("End: ***********************\n");
> }
> 
> $ dtrace -s printaddr.d
> 
>   3  36888                nfs3_access:entry
> Start: ***********************
> vnode_t: cc804300
> vdata_t: cd0f5c48
> r_path: 0
> r_unlname: 0
> End: ***********************
> 
> I traced down r_rpath to create_rnode, and it looks like it''s only
set if
> a failover mount is in use. When I opengrok or r_unldvp, it shows up in 
Correct.  The r_path is only used when it is a replicated mount.
> the NFSv3 inactive, rename and remove routines, and I wasn''t able
to spot
> the location where r_unlname originalyl gets set (poor eyes I recon). Does 
The r_unlname stands for "unlinked name".  This is used in the case
that a file is open at the client and it is be removed or is the
target for a rename.  The renamed file usually takes the form of .nfsXXXX
and is commonly referred to as "silly rename".
> anyone happen to know if there is a way to get the full path to the file 
> (or directory) being checked in nfs3_access?
There is a path in the vnode v_path that is maintained for a file but
there are cases where that path will not be entirely correct but it is
currently the best available.

Spencer

On Mon, 17 Apr 2006, Spencer Shepler wrote:
>> the NFSv3 inactive, rename and remove routines, and I wasn''t
able to spot
>> the location where r_unlname originalyl gets set (poor eyes I recon).
Does
>
> The r_unlname stands for "unlinked name".  This is used in the
case
> that a file is open at the client and it is be removed or is the
> target for a rename.  The renamed file usually takes the form of .nfsXXXX
> and is commonly referred to as "silly rename".
Thanks for the cool explanation!
>> anyone happen to know if there is a way to get the full path to the
file
>> (or directory) being checked in nfs3_access?
>
> There is a path in the vnode v_path that is maintained for a file but
> there are cases where that path will not be entirely correct but it is
> currently the best available.
Based on my testing, v_path seems to contain a directory, and not the full 
pathname. :( Is the filename stored anywhere by any chance?

Thanks,
- Ryan
--
UNIX Administrator
http://daemons.net/~matty

>
> Based on my testing, v_path seems to contain a directory, and not the 
> full pathname. :( Is the filename stored anywhere by any chance?
>
Matt,

Although  not completely reliable, v_path is still the best bet,
Call to nfs3_access need not necessarily be to the file itself.

Here is what I used to print the file name

#  dtrace -n nfs3_access:entry''{trace(stringof(((vnode_t 
*)arg0)->v_path)); printf(" :: VNODE 0x%p", arg0)}''

$ ls -l  zfs_overview.pdf
gave
 1  52877                nfs3_access:entry   
/net/ssaesrv/export/scratch/nagki :: VNODE 0xffffffff8b47a240
  ....... (approximately 8 lines of same info)
  1  52877                nfs3_access:entry   
/net/ssaesrv/export/scratch/nagki :: VNODE 0xffffffff8b47a240

Most probably the calls to dnlc via nfs3_lookup_dnlc called from nfs3_lookup

BUT
$ cat zfs_overview.pdf
actually located the file and the vnode for it.
1  52877                nfs3_access:entry   
/net/ssaesrv/export/scratch/nagki/zfs_overview.pdf :: VNODE 
0xffffffff8b46ecc0

Regards
Kiran