FreeBSD r364421

sysctl vfs.cache_fast_lookup=0
stat /tmp/test

Edited to remove:
- spurious indent due to tail calls
- spurious indent due to ifunc
- interrupt handling

dtrace script:
#pragma D option flowindent                       

syscall::fstatat:entry
/curthread->td_ucred->cr_uid == 770/
{
	self->follow = 1;
}

syscall::fstatat:return
{
	self->follow = 0;
}

fbt:::entry,
fbt:::return
/self->follow/
{}

output:
-> sys_fstatat                           
  -> kern_statat                         
    -> namei                             
      -> uma_zalloc_arg                  
      <- uma_zalloc_arg                  
      -> copyinstr_smap                
      <- copyinstr_smap                
      -> cache_fplookup                
      <- cache_fplookup                
      -> pwd_hold                      
      <- pwd_hold                      
      -> namei_handle_root             
        -> vrefact                     
        <- vrefact                     
      <- namei_handle_root             
      -> lookup                        
        -> _vn_lock                    
          -> vop_lock                  
            -> lockmgr_slock           
            <- lockmgr_slock           
          <- vop_lock                  
        <- _vn_lock                  
        -> zfs_cache_lookup          
          -> vfs_cache_lookup        
            -> vn_dir_check_exec     
              -> zfs_freebsd_access  
                -> zfs_freebsd_fastaccesschk_execute 
                <- zfs_freebsd_fastaccesschk_execute 
              <- zfs_freebsd_access  
            <- vn_dir_check_exec     
            -> cache_lookup          
              -> memcmp              
              <- memcmp              
              -> vget_prep_smr       
              <- vget_prep_smr       
              -> vget_finish         
                -> _vn_lock          
                  -> vop_lock        
                    -> lockmgr_slock 
                    <- lockmgr_slock 
                  <- vop_lock        
                <- _vn_lock        
              <- vget_finish       
            <- cache_lookup        
          <- vfs_cache_lookup      
        <- zfs_cache_lookup          
        -> vfs_busy              
        <- vfs_busy              
        -> vput                  
          -> vop_unlock          
            -> lockmgr_unlock    
            <- lockmgr_unlock    
          <- vop_unlock          
        <- vput                
        -> vput                
          -> vop_unlock        
            -> lockmgr_unlock  
            <- lockmgr_unlock  
          <- vop_unlock        
        <- vput              
        -> vrefact           
        <- vrefact           
        -> vfs_cache_root    
          -> _vn_lock        
            -> vop_lock      
              -> lockmgr_slock 
              <- lockmgr_slock 
            <- vop_lock      
          <- _vn_lock      
        <- vfs_cache_root  
        -> vfs_unbusy      
        <- vfs_unbusy      
        -> _vn_lock        
          -> crossmp_vop_lock1 
          <- crossmp_vop_lock1 
        <- _vn_lock        
        -> vput            
          -> crossmp_vop_unlock 
          <- crossmp_vop_unlock 
        <- vput            
        -> vfs_cache_lookup 
          -> vn_dir_check_exec 
            -> tmpfs_access 
            <- tmpfs_access 
          <- vn_dir_check_exec 
          -> cache_lookup  
            -> memcmp      
            <- memcmp      
            -> vget_prep_smr 
            <- vget_prep_smr 
            -> vget_finish 
              -> _vn_lock  
                -> vop_lock 
                  -> lockmgr_slock 
                  <- lockmgr_slock 
                <- vop_lock 
              <- _vn_lock 
            <- vget_finish 
          <- cache_lookup 
        <- vfs_cache_lookup 
        -> vput          
          -> vop_unlock  
            -> lockmgr_unlock 
            <- lockmgr_unlock 
          <- vop_unlock  
        <- vput        
      <- lookup        
      -> uma_zfree_arg 
        -> pmap_kextract 
        <- pmap_kextract 
        -> _vm_phys_domain 
        <- _vm_phys_domain 
      <- uma_zfree_arg 
      -> pwd_drop      
      <- pwd_drop      
    <- namei           
    -> tmpfs_stat      
      -> memset_erms 
      <- memset_erms 
      -> priv_check_cred_vfs_generation 
      <- priv_check_cred_vfs_generation 
    <- tmpfs_stat    
    -> NDFREE_PNBUF  
    <- NDFREE_PNBUF  
    -> vput          
      -> vput_final  
        -> tmpfs_need_inactive 
        <- tmpfs_need_inactive 
        -> vop_unlock 
          -> lockmgr_unlock 
          <- lockmgr_unlock 
        <- vop_unlock 
        -> vdropl  
        <- vdropl  
      <- vput_final 
    <- vput          
  <- kern_statat 
  -> copyout_smap_erms 
  <- copyout_smap_erms 
<- sys_fstatat