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400 Bad Request - NFS attribute cache problem

From: Devin Bougie <dab66_at_mail.lepp.cornell.edu>
Date: 2007-04-13 02:25:24 CEST


We get the following error when running an svn checkout on SL4
(RHEL4) from an nfs-mounted directory:
REPORT request failed on '/svn/!svn/vcc/default'
svn: REPORT of '/svn/!svn/vcc/default': 400 Bad Request (https://

In looking at system call traces for SL3 and SL4 clients checking
out --here's where we think it's going pear-shaped, about 1800
syscalls in:

open("bmad/.svn/tmp/tempfile.tmp", O_RDWR|O_CREAT|O_EXCL, 0666) = 3
write(3, "<S:update-report send-all=\"true\""..., 218) = 218
-fstat64(3, {st_mode=S_IFREG|0644, st_size=218, ...}) = 0
+fstat64(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0

'-' is SL3, '+' is SL4. So it's opening a temporary file under
the working area, writing 218 bytes to it, and immediately
statting it. SL3 gets 218 bytes, SL4 gets 0. On SL3, the next
step is to rewind the file, read 218 bytes, and send something
(probably the same 218 bytes SSL encrypted) to the svn server.
With the attribute cache on, the answer to the fstat64 comes out
of the cache; with it off, the write has to commit and the fstat64
round-trips to the server, so this is all looking consistent with
an NFS attribute cache problem on SL4.

doing a second fstat gets the right answer, so
that could be a workaround if we can identify the right spot in the
svn code. (We suppose it's possible this is timing related, in which
case the
second stat might not *reliably* fix the problem...)

Here is a test program to demonstrate the bug.

dsr_lnxcu9% cat svnbug.c
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

#ifndef TESTSIZE
#define TESTSIZE 52

int main(int argc, char** argv)
     char s[TESTSIZE+1];
     struct stat st1, st2;
     int r;
     ssize_t len;

     int fd = open("tmpfile.xyzzy", O_RDWR|O_CREAT|O_EXCL, 0666);

     if (fd < 0) {
     memset(s, 'x', TESTSIZE);
     len = write(fd, s, TESTSIZE);
     if (len < 0) {
     r = fstat(fd, &st1);
     if (0 != r) {
     r = fstat(fd, &st2);
     if (0 != r) {
     printf("len = %zd, st1 = %zd, st2 = %zd\n",
            len, st1.st_size, st2.st_size);


     return 0;
dsr_lnxcu9% gcc svnbug.c
dsr_lnxcu9% ~/a.out
len = 52, st1 = 52, st2 = 52
dsr_lnxcu9% cd /cdat/tem/dsr
dsr_lnxcu9% ~/a.out
len = 52, st1 = 0, st2 = 52

Here is a bugzilla report with redhat:

And here are others with the same problem:

Any suggestions or workaround would be greatly appreciated.

Many thanks,


Devin Bougie
Laboratory for Elementary-Particle Physics

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Received on Fri Apr 13 02:25:50 2007

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