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Hi
I'm on Debian Squeeze using NFSv4 (2.6.32 / 1.1.2). Groups ares stored in
LDAP and one contains a space. If I want to chgrp a file, the chown system
call gets stuck and I get an kernel "hung_task" backtrace:
[76920.364077] INFO: task chown:31709 blocked for more than 120 seconds.
[76920.364781] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[76920.365894] chown D 0000000000000000 0 31709 28415 0x00000004
[76920.365900] ffffffff814611f0 0000000000000086 0000000000000000 ffff88000886de88
[76920.365906] ffff88000886dde8 ffffffff810f6211 000000000000f9e0 ffff88000886dfd8
[76920.365910] 0000000000015780 0000000000015780 ffff88003ed269f0 ffff88003ed26ce8
[76920.365914] Call Trace:
[76920.365927] [<ffffffff810f6211>] ? path_to_nameidata+0x15/0x37
[76920.365933] [<ffffffff811035cd>] ? mntput_no_expire+0x23/0xee
[76920.365940] [<ffffffff812fb99b>] ? __mutex_lock_common+0x122/0x192
[76920.365945] [<ffffffff810f9c1c>] ? user_path_at+0x52/0x79
[76920.365948] [<ffffffff812fbac3>] ? mutex_lock+0x1a/0x31
[76920.365954] [<ffffffff810ed746>] ? chown_common+0x5b/0x7c
[76920.365958] [<ffffffff812fe9f6>] ? do_page_fault+0x2e0/0x2fc
[76920.365962] [<ffffffff810ed982>] ? sys_fchownat+0x53/0x70
[76920.365967] [<ffffffff81010b42>] ? system_call_fastpath+0x16/0x1b
[77240.440046] nfs: server buildserv-next not responding, still trying
[95664.836086] nfs: server buildserv-next not responding, still trying
[96568.599435] nfs: server buildserv-next OK
So I backported the Debian nfs-utils 1.1.4 and updated the kernel to the
squeeze-backports version (2.6.39).
The backtrace is now gone, but the chgrp process is still stuck.
The client rpc.idmapd seems to be fine:
Aug 26 20:41:41 kvm-auth rpc.idmapd[973]: nfs4_gid_to_name: calling nsswitch->gid_to_name
Aug 26 20:41:41 kvm-auth rpc.idmapd[973]: nfs4_gid_to_name: nsswitch->gid_to_name returned 0
Aug 26 20:41:41 kvm-auth rpc.idmapd[973]: nfs4_gid_to_name: final return value is 0
Aug 26 20:41:41 kvm-auth rpc.idmapd[973]: Client 0: (group) id "1094" -> name "Domain Administrators@xxxxxxxxxxxxxxx"
On the server side I see idmapd errors in the daemon.log (every 2 minutes,
so I guess the backtrace is just suppressed - same as the previous 120 sec
timeout):
Aug 26 20:27:48 buildserv-next rpc.idmapd[16848]: nfsdcb: authbuf=* authtype=group
Aug 26 20:27:48 buildserv-next rpc.idmapd[16848]: nfsdcb: bad name in upcall
There is an invalid check in the idmapd code, which converts the octal
encoded values back to the original characters (see attached patch).
What I don't know is how to implement the "real" error handling. I don't
think the client process should be stuck forever, just because the server
fails to find the encoded name.
Regards,
Jan-Marek Glogowski
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idmapd: correctly convert octal encoded field values
We want to check for (unsigned char) -1.
--- nfs-utils-1.2.4.orig/utils/idmapd/idmapd.c
+++ nfs-utils-1.2.4/utils/idmapd/idmapd.c
@@ -925,9 +925,9 @@ getfield(char **bpp, char *fld, size_t f
if (*bp == '\\') {
if ((n = sscanf(bp, "\\%03o", &val)) != 1)
return (-1);
- if (val > (char)-1)
+ if (val > UCHAR_MAX)
return (-1);
- *fld++ = (char)val;
+ *fld++ = val;
bp += 4;
} else {
*fld++ = *bp;
