Red Hat Bugzilla – Bug 157436
nfs client hangs
Last modified: 2007-11-30 17:11:05 EST
Description of problem:
Heavy nfs read access to many small files causes the nfs client to hang for
future accesses to that partition for this client machine. Access to that
partition even by df no longer is possible for this client. Access by this
client to other partitions on the same or other servers works. Access from
other clients to the server's partition that the particular client is having
problems with works.
This never happens for Red Hat 9 clients buts happens for Fedora Core 3
clients and Fedora Core 4 test 3 clients.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1.Have many files on a server in multiple subdirectories (~1MB per file, ~1000
files per subdirectory, ~1000 subdirectores)
2.Have script on client read these files and do some small computation like
search for a string in each file. Print to screen when you go to another
3. Within a few to 10 minutes, the script will stop running even though it is
far from done (usually before 300 subdirectories). When you do df in another
window the df will not complete or will other attempts to access files on that
partition from this client machine
Works for Red Hat 9, fails for Fedora Core 3 and Fedora Core 4 test 3.
Script stops before completion and access to that partition is not possible
from that client anymore, until after reboot.
Access to that partition is possible from other machines so it doesn't appear
to be a problem on the server.
The script would complete and access to that partition would still be possible
without rebooting the client machine.
When the hang occurs, could you get a system trace my
doing a "echo t > /proc/sysrq-trigger"
(Note: you may have to enable System Request debugging by
echo 1 > /proc/sys/kernel/sysrq or editing /etc/sysctl.conf)
Also if its feeble, could you post a bzip2 binary tethereal trace
(i.e. tethereal -w /tmp/data.pcap) of the problem?
Created attachment 114647 [details]
tracing enabled, machine rebooted, script run which causes nfs client to hang
for the partition being accessed (hang occurred)
I appears you may not have SysReq debugging enabled since
there was no backtracks in the messages file you posted.
Please enable the debugging (see comment #) and trying
it again. Note you should see output similar to :
lockd S 00000000 112 3236 1 3780 3235 (L-TLB)
Call Trace: [<c0124124>] schedule [kernel] 0x2f4 (0xd342bed8)
[<c01390f5>] __group_send_sig_info [kernel] 0x325 (0xd342bee8)
[<c01351dc>] schedule_timeout [kernel] 0xbc (0xd342bf1c)
[<e098726a>] svc_recv_Rsmp_4f7fb8d3 [sunrpc] 0x3ca (0xd342bf54)
[<e09a0912>] .rodata.str1.1 [lockd] 0x121 (0xd342bfac)
[<e09983cf>] lockd [lockd] 0x15f (0xd342bfc4)
[<e0998270>] lockd [lockd] 0x0 (0xd342bfe0)
[<c01095ad>] kernel_thread_helper [kernel] 0x5 (0xd342bff0)
cupsd R 00000000 0 3780 1 3236 (NOTLB)
Call Trace: [<c01591c4>] __alloc_pages [kernel] 0xb4 (0xdbe35e8c)
[<c0124124>] schedule [kernel] 0x2f4 (0xdbe35ea0)
[<c0135185>] schedule_timeout [kernel] 0x65 (0xdbe35ee4)
[<c0135110>] process_timeout [kernel] 0x0 (0xdbe35f04)
[<c017986b>] do_select [kernel] 0x13b (0xdbe35f1c)
[<c0179d0e>] sys_select [kernel] 0x34e (0xdbe35f60)
[<c01ffa1b>] audit_intercept [kernel] 0x4b (0xdbe35fac)
when the debugging is configured correctly.
Created attachment 114731 [details]
more debugging info
This appears to be a system trace of the server and the NFS server (i.e. nfsds)
seem to be doing fine but I can not see where the client process are hung.
So you post a client system trace that would allow me to see where those
process are hung.
But there are a couple of anomalies I see. The first one is:
rpc.idmapd: nfsdreopen: Opening 'ib/nfs/rpc_pipefs/nfs' failed: errno 2 (No such
file or directory)
rpc.idmapd: nfsdreopen: Opening '' failed: errno 2 (No such file or directory)
Which is ok since idmapd has to start before the nfs server, but what I don't see
is the nfs init script sending idmapd a signal telling it to reopen those files
because the server just started. What nfs-utils version are you using?
The second thing I see is the process scsi_eh_1 is in the scsi_error_handler
scsi_eh_1 S C4120160 3676 436 1 437 423 (L-TLB)
f7927f84 00000046 c011b2ea c4120160 f7b75020 c0401200 00000002 00000020
f4e8f1c0 000f4200 00000000 00000000 f791a674 f791a550 c035ac00 c4118160
f4f83400 000f4200 00000000 f7927000 c014c6ff f7af0ebc 00000000 f7ba9ea8
[<f884a214>] .text.lock.scsi_error+0x3b/0x47 [scsi_mod]
[<f8849c5f>] scsi_error_handler+0x0/0x18c [scsi_mod]
Which may or may not be normal...
scsi_eh_1 is an error handler thread, currently idle. This is normal. You will
see these on any 2.6 system that has a SCSI adapter. It does not indicate a SCSI
error has occurred. Best to look in /var/log/messages for those indications.
I modified the csh script that performs the nfs accesses that causes nfs to
hang on the client machine. I added the trigger line, echo t > /proc/sysrq-
trigger, before the line that reads the data. I tested it several times and
the scripts now complete (although slower and creates a
massive /var/log/message file). If I remove the line, it runs faster but
after a while nfs will hang on the client. What should I do to help you get
the debugging info you need?
There are a little over a thousand of files in each directory where each file
is around 1MB.
foreach d (/project/nas1a/UHRR_products/chips/[0-9][0-9][0-9])
echo "Checking $d ..."
foreach f ($d/*.fc)
echo t > /proc/sysrq-trigger
set n = `hexdump -n 64 $f | grep "0000 ffc0" | wc -l`
if ($n > 0) then
echo "NaN found in $f"