kern/132068: page fault when using ZFS over NFS on 7.1-RELEASE/amd64

[Edward Fisk]

The following reply was made to PR kern/132068; it has been noted by GNATS.

From: "Edward Fisk" <7ogcg7g02 at sneakemail.com>
To: bug-followup at freebsd.org
Cc:  
Subject: Re: kern/132068: page fault when using ZFS over NFS on
 7.1-RELEASE/amd64
Date: 24 Feb 2009 20:25:13 -0000

 (kgdb) frame 8
 #8  0xffffffff80651673 in nfsrv_readdirplus (nfsd=0xffffff0041546700, slp=0xffffff0079a7ad00, td=0xffffff0003793370, 
     mrq=0xffffffffdd9d6b00) at /usr/src/sys/nfsserver/nfs_serv.c:3645
 3645				nfhp->fh_fsid =
 (kgdb) p *nvp
 $1 = {v_type = VBAD, v_tag = 0xffffffff807e5627 "none", v_op = 0xffffffff80a18220, v_data = 0x0, v_mount = 0x0, v_nmntvnodes = {
     tqe_next = 0xffffff00529b2bd0, tqe_prev = 0xffffff000af92028}, v_un = {vu_mount = 0x0, vu_socket = 0x0, vu_cdev = 0x0, 
     vu_fifoinfo = 0x0, vu_yield = 0}, v_hashlist = {le_next = 0x0, le_prev = 0x0}, v_hash = 0, v_cache_src = {lh_first = 0x0}, 
   v_cache_dst = {tqh_first = 0x0, tqh_last = 0xffffff0051130258}, v_dd = 0x0, v_cstart = 0, v_lasta = 0, v_lastw = 0, v_clen = 0, 
   v_lock = {lk_object = {lo_name = 0xffffffffdd978d4d "zfs", lo_type = 0xffffffffdd978d4d "zfs", lo_flags = 70844416, 
       lo_witness_data = {lod_list = {stqe_next = 0x0}, lod_witness = 0x0}}, lk_interlock = 0xffffffff80ab2c80, lk_flags = 64, 
     lk_sharecount = 0, lk_waitcount = 0, lk_exclusivecount = 0, lk_prio = 80, lk_timo = 51, lk_lockholder = 0xffffffffffffffff, 
     lk_newlock = 0x0}, v_interlock = {lock_object = {lo_name = 0xffffffff8085132a "vnode interlock", 
       lo_type = 0xffffffff8085132a "vnode interlock", lo_flags = 16973824, lo_witness_data = {lod_list = {stqe_next = 0x0}, 
         lod_witness = 0x0}}, mtx_lock = 4, mtx_recurse = 0}, v_vnlock = 0xffffff0051130290, v_holdcnt = 1, v_usecount = 1, 
   v_iflag = 128, v_vflag = 0, v_writecount = 0, v_freelist = {tqe_next = 0xffffff00529b2bd0, tqe_prev = 0xffffffff80aca090}, 
   v_bufobj = {bo_mtx = 0xffffff00511302e0, bo_clean = {bv_hd = {tqh_first = 0x0, tqh_last = 0xffffff0051130350}, bv_root = 0x0, 
       bv_cnt = 0}, bo_dirty = {bv_hd = {tqh_first = 0x0, tqh_last = 0xffffff0051130370}, bv_root = 0x0, bv_cnt = 0}, 
     bo_numoutput = 0, bo_flag = 0, bo_ops = 0xffffffff80a336a0, bo_bsize = 131072, bo_object = 0x0, bo_synclist = {le_next = 0x0, 
       le_prev = 0x0}, bo_private = 0xffffff00511301f8, __bo_vnode = 0xffffff00511301f8}, v_pollinfo = 0x0, v_label = 0x0, 
   v_lockf = 0x0}
 (kgdb) p *nvp->v_mount
 Cannot access memory at address 0x0
 
 ---
 > If nvp is NULL it's likely a bug in zfs_zget(). Looks like the zfs
 > version in head has updated zfs_zget() which might fix the issue.
 
 Thanks for the tip.  I will try building a kernel with revision 1.15.2.3 of zfs_znode.c and see what happens.