Hello *,
creating a file in the directory exported by the NFS server
sometimes returns an error - "resource temporarily unavailable",
when a client on importing computer is keeping reading that file.
serv:~# cat /etc/exports
/home/me/data-t cli(ro,sync,no_subtree_check)
serv:~# systemctl restart nfs-kernel-server
cli:~# cat /etc/fstab
...
mhfpklytsserv:/home/me/data-t /home/me/dt nfs noauto,ro,noac,user 0 0
me@cli:~$ mount dt
me@cli:~$ mount
...
serv:/home/me/data-t on /home/me/dt type nfs4
(ro,nosuid,nodev,noexec,relatime,sync,vers=4.0,rsize=1048576,wsize=1048576,namlen=255,acregmin=0,acregmax=0,acdirmin=0,acdirmax=0,hard,noac,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=192.168.209.174,local_lock=none,addr=192.168.238.113,user=me)
It could be provoked in a few minutes by running on the server
serv:~$ while : ; do date > data-t/now.txt; sleep 1; done
while on the client computer
me@cli:~$ while : ; do cat dt/now.txt; sleep 1; done
After a while (it's unpredictable might take up 10 minutes or a few seconds,
but in average about 2 minutes)
on the server I get:
data-t/now.txt: Resource temporarily unavailable
Lesser 'sleep', of 0.2 for ex., doesn't necessarily make the error appear
quicker.
Also it doesn't depend whether a directory is exported read-only or read-write.
But without reading client the error never appears.
To narrow down the case a bit I made a test on 'C' for the server
which does the same thing as the script above - just writing down a date in the
same file
- but checking an error on creating a file and writing to it.
Sometimes error appears just in a few seconds:
serv:~$ date;./tnfs-open data-t/now.txt ;date
Mon Aug 1 18:58:23 CEST 2016
open fd=-1 errno=11 -> Resource temporarily unavailable
Mon Aug 1 18:58:25 CEST 2016
serv:~$ errno 11
EAGAIN 11 Resource temporarily unavailable
I am at a loss :(
my system on the server and the client computes is the same Debian 8.5
:~$ dpkg -l 'nfs*'|grep '^ii'
ii nfs-common 1:1.2.8-9 amd64 NFS support files common to
client and server
ii nfs-kernel-server 1:1.2.8-9 amd64 support for NFS kernel server
:~$ dpkg -l 'systemd*'|grep '^ii'
ii systemd 215-17+deb8u4 amd64 system and service manager
ii systemd-sysv 215-17+deb8u4 amd64 system and service manager - SysV
links
:~$ dpkg -l 'linux-*'|grep '^ii'
ii linux-base 3.5 all
Linux image base package
ii linux-compiler-gcc-4.8-x86 3.16.7-ckt25-2+deb8u3 amd64
Compiler for Linux on x86 (meta-package)
ii linux-headers-3.16.0-4-amd64 3.16.7-ckt25-2+deb8u3 amd64
Header files for Linux 3.16.0-4-amd64
ii linux-headers-3.16.0-4-common 3.16.7-ckt25-2+deb8u3 amd64
Common header files for Linux 3.16.0-4
ii linux-headers-amd64 3.16+63 amd64
Header files for Linux amd64 configuration (meta-package)
ii linux-image-3.16.0-4-amd64 3.16.7-ckt25-2+deb8u3 amd64
Linux 3.16 for 64-bit PCs
ii linux-image-amd64 3.16+63 amd64
Linux for 64-bit PCs (meta-package)
ii linux-kbuild-3.16 3.16.7-ckt20-1 amd64
Kbuild infrastructure for Linux 3.16
ii linux-libc-dev:amd64 3.16.7-ckt25-2+deb8u3 amd64
Linux support headers for userspace development
Am I wrong with NFS options ?
But it was working on Debian 7 (and perhaps 6/5) and it began in May I upgraded
to Debian 8.
Thanks,
Andrey
PS:
I already posted the question to the list in June
https://lists.debian.org/debian-user/2016/06/msg00738.html
But at that time I was looking for some kind of imposed limits.
PPS:
For those who would rather try that 'C' test above
cat tnfs-open.c
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <time.h>
int main (int argc, char *argv[])
{
int fd,err,e,sec,ms;
time_t tm;
struct timespec tdly={.tv_sec=1, .tv_nsec=0};
char *ept=NULL,*bf=NULL;
if (argc < 2) {
fprintf(stderr, "Usage: %s file-to-overwrite [milliseconds]\n", argv[0]);
exit(1);
}
if (argc > 2) {
ms=strtol(argv[2],&ept,10);
if (ept==argv[2]) {
fprintf(stderr, "interval should be integer number of milliseconds\n",
ms);
exit(1);
} else {
fprintf(stderr, "interval=%d ms\n", ms);
sec=ms/1000;
tdly.tv_sec=sec;
tdly.tv_nsec=(ms-sec*1000)*1000000;
}
}
for (;;) {
tm=time(NULL);
bf=ctime(&tm);
fd=open(argv[1], O_WRONLY|O_CREAT|O_TRUNC, 0666);
if (fd<0) {
err=errno;
fprintf(stderr, "open fd=%d errno=%d -> %s\n", fd, err,strerror(err));
exit(2);
}
e=write(fd, bf, strlen(bf));
if (e<0) {
err=errno;
fprintf(stderr, "write error=%d errno=%d\n", e, err,strerror(err));
exit(3);
}
close(fd);
nanosleep(&tdly,NULL);
}
}
