Description of problem:

I noticed that kernel 2.6.18-128.1.16.el5 reports file type of /proc/1/task/1/
as DT_UNKNOWN, while vanilla kernel 2.6.31-rc2 reports it as DT_DIR.

Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1. Build the test program and run as root user.

----- Start of test program -----
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <dirent.h>

static char path[8192] = "/proc/1";

static void scan_dir(void)
{
        struct dirent **namelist;
        int n = scandir(path, &namelist, 0, 0);
        int len;
        int i;
        if (n < 0)
                return;
        len = strlen(path);
        for (i = 0; i < n; i++) {
                const unsigned char type = namelist[i]->d_type;
		const char *name = namelist[i]->d_name;
                snprintf(path + len, sizeof(path) - len - 1, "/%s", name);
                if (type == DT_DIR &&strcmp(name, ".") && strcmp(name, ".."))
			scan_dir();
		else if (type == DT_REG)
			printf("FILE: %s\n", path);
                else if (type == DT_UNKNOWN)
                        printf("Unknown type: %s\n", path);
                free((void *) namelist[i]);
        }
        free((void *) namelist);
}

int main(int argc, char *argv[])
{
	scan_dir();
	return 0;
}
----- End of test program -----
  
Actual results:
----- Test result on 2.6.18-128.1.16.el5 -----
Unknown type: /proc/1/task/1
FILE: /proc/1/environ
FILE: /proc/1/auxv
FILE: /proc/1/status
FILE: /proc/1/cmdline
FILE: /proc/1/stat
FILE: /proc/1/statm
FILE: /proc/1/maps
FILE: /proc/1/mem
FILE: /proc/1/mounts
FILE: /proc/1/mountstats
FILE: /proc/1/smaps
FILE: /proc/1/attr/current
FILE: /proc/1/attr/prev
FILE: /proc/1/attr/exec
FILE: /proc/1/attr/fscreate
FILE: /proc/1/attr/keycreate
FILE: /proc/1/attr/sockcreate
FILE: /proc/1/wchan
FILE: /proc/1/schedstat
FILE: /proc/1/cpuset
FILE: /proc/1/oom_score
FILE: /proc/1/oom_adj
FILE: /proc/1/loginuid
FILE: /proc/1/limits
FILE: /proc/1/coredump_filter

Expected results:
Something like below output.
----- Test result on 2.6.31-rc2 -----
FILE: /proc/1/task/1/environ
FILE: /proc/1/task/1/auxv
FILE: /proc/1/task/1/status
FILE: /proc/1/task/1/personality
FILE: /proc/1/task/1/limits
FILE: /proc/1/task/1/sched
FILE: /proc/1/task/1/syscall
FILE: /proc/1/task/1/cmdline
FILE: /proc/1/task/1/stat
FILE: /proc/1/task/1/statm
FILE: /proc/1/task/1/maps
FILE: /proc/1/task/1/mem
FILE: /proc/1/task/1/mounts
FILE: /proc/1/task/1/mountinfo
FILE: /proc/1/task/1/clear_refs
FILE: /proc/1/task/1/smaps
FILE: /proc/1/task/1/pagemap
FILE: /proc/1/task/1/wchan
FILE: /proc/1/task/1/stack
FILE: /proc/1/task/1/schedstat
FILE: /proc/1/task/1/latency
FILE: /proc/1/task/1/oom_score
FILE: /proc/1/task/1/oom_adj
FILE: /proc/1/task/1/loginuid
FILE: /proc/1/task/1/sessionid
FILE: /proc/1/task/1/make-it-fail
FILE: /proc/1/fdinfo/10
FILE: /proc/1/net/ip6_flowlabel
FILE: /proc/1/net/rt6_stats
FILE: /proc/1/net/ipv6_route
FILE: /proc/1/net/if_inet6
FILE: /proc/1/net/dev_snmp6/eth0
FILE: /proc/1/net/dev_snmp6/lo
FILE: /proc/1/net/snmp6
FILE: /proc/1/net/sockstat6
FILE: /proc/1/net/udplite6
FILE: /proc/1/net/raw6
FILE: /proc/1/net/mcfilter6
FILE: /proc/1/net/igmp6
FILE: /proc/1/net/anycast6
FILE: /proc/1/net/tcp6
FILE: /proc/1/net/udp6
FILE: /proc/1/net/packet
FILE: /proc/1/net/unix
FILE: /proc/1/net/snmp
FILE: /proc/1/net/netstat
FILE: /proc/1/net/sockstat
FILE: /proc/1/net/udp
FILE: /proc/1/net/tcp
FILE: /proc/1/net/raw
FILE: /proc/1/net/ip_mr_cache
FILE: /proc/1/net/ip_mr_vif
FILE: /proc/1/net/udplite
FILE: /proc/1/net/mcfilter
FILE: /proc/1/net/igmp
FILE: /proc/1/net/rt_cache
FILE: /proc/1/net/route
FILE: /proc/1/net/arp
FILE: /proc/1/net/dev_mcast
FILE: /proc/1/net/ptype
FILE: /proc/1/net/softnet_stat
FILE: /proc/1/net/dev
FILE: /proc/1/net/protocols
FILE: /proc/1/net/netlink
FILE: /proc/1/net/stat/ndisc_cache
FILE: /proc/1/net/stat/rt_cache
FILE: /proc/1/net/stat/arp_cache
FILE: /proc/1/environ
FILE: /proc/1/auxv
FILE: /proc/1/status
FILE: /proc/1/personality
FILE: /proc/1/limits
FILE: /proc/1/sched
FILE: /proc/1/syscall
FILE: /proc/1/cmdline
FILE: /proc/1/stat
FILE: /proc/1/statm
FILE: /proc/1/maps
FILE: /proc/1/mem
FILE: /proc/1/mounts
FILE: /proc/1/mountinfo
FILE: /proc/1/mountstats
FILE: /proc/1/clear_refs
FILE: /proc/1/smaps
FILE: /proc/1/pagemap
FILE: /proc/1/wchan
FILE: /proc/1/stack
FILE: /proc/1/schedstat
FILE: /proc/1/latency
FILE: /proc/1/oom_score
FILE: /proc/1/oom_adj
FILE: /proc/1/loginuid
FILE: /proc/1/sessionid
FILE: /proc/1/make-it-fail
FILE: /proc/1/coredump_filter

Additional info:
I'm using CentOS5.3 , but this problem should be reproducible on RHEL5.3 .
Please test on RHEL5.3 .