[OpenAFS-devel] kernel debug info for iput issue...

[Neulinger, Nathan]

I added some debug tracing to afs/LINUX/osi_misc.c and afs/LINUX/osi_vfs.h.

I've determined that it occurs when loading the root page for that server.
It increases by approximately 9-12 each time that page is loaded. Simply
killing and restarting the web server increases it by 1 or 2. 

i_count for 0xd0340a28/1831075970 at ../afs/afs_vcache.c:2374 is 117
i_count++ for 0xd0340a28/1831075970 at ../afs/afs_vcache.c:2374 now 118

that's osi_vnhold in FindVCache

i_count for 0xd0340a28/1831010434 at ../afs/afs_osidnlc.c:246 is 118
i_count++ for 0xd0340a28/1831010434 at ../afs/afs_osidnlc.c:246 now 119
tvc->mvstat = 2 in afs_vnop_lookup
osi_iput: i_count for 0xd0340a28/1831010434 at ../afs/osi_misc.c:352, is 119
i_count for 0xd0340a28/1831010434 at ../afs/osi_misc.c:377, is 119
i_count-- for 0xd0340a28/1831010434 at ../afs/osi_misc.c:380, now 118

That's osi_iput called from osi_dnlc_lookup called from afs_vnop_lookup

i_count for 0xd0340a28/1831010434 at ../afs/afs_vcache.c:2374 is 118
i_count++ for 0xd0340a28/1831010434 at ../afs/afs_vcache.c:2374 now 119
i_count for 0xd0340a28/1831075970 at ../afs/afs_osidnlc.c:246 is 119
i_count++ for 0xd0340a28/1831075970 at ../afs/afs_osidnlc.c:246 now 120


It sure looks to me like the reference obtained by FindVCache is being lost.
Both FindVCache and osi_dncl_lookup  are incrementing the reference count,
yet osi_iput is only being called after the afs_vnop_lookup and never
cancelling out the reference from FindVCache.

For other inodes (stripped from above output) it looks fine. I typically see
a FindVCache for those, shortly followed by an osi_iput that decrements the
refcount. 

Look at this from VNOPS/afs_vnop_lookup.c

    *avcp = tvc;  /* maybe wasn't initialized, but it is now */
#ifdef AFS_LINUX22_ENV
    if (tvc) {
      if (tvc->mvstat == 2) { /* we don't trust the dnlc for root vcaches */
        AFS_RELE(tvc);
        *avcp = 0;
      }
      else {
        code = 0;
        hit = 1;
        goto done;
      }
    }
#else /* non - LINUX */

That release is definately taking place... 

-- Nathan

------------------------------------------------------------
Nathan Neulinger                       EMail:  nneul@umr.edu
University of Missouri - Rolla         Phone: (573) 341-4841
Computing Services                       Fax: (573) 341-4216