Thread: NFS timeout problem

some code maybe:

Code:

#include        <sys/stat.h>
#include        <signal.h>

void timed_out(){}

int main()
{
        int timeout = 5,check_in = 0;
        int *ch_res = NULL;
        struct sigaction action;

        bzero(&action, sizeof(action));
        action.sa_handler = timed_out;
        action.sa_flags = 0;
        sigaction(SIGALRM, &action, 0);

        char *h = "/tmp/test/dir/";

        alarm(timeout);
        ch_res = (int*)malloc(sizeof(int) * 1);
        printf("set timeout; attempting to chdir to %s\n",h);
        //try and chdir to broken nfs directory
        ch_res[0] = chdir(h);
        if(ch_res)printf("got result from chdir - %d\n",ch_res[0]);
        alarm(0);

        if(!ch_res)
        {
                printf("timeout whilst changing to directory %s - NFS problem?\n",h);
                free(ch_res);
                exit(1);
        }

                if (ch_res[0] < 0)
                {
                        printf("Creating directory %s\n",h);

                        if(mkdir(h, 0755))
                        {
                                printf("Error making directory %s\n",h);
                                exit(1);
                        }
                        else
                        {
                                printf("Made directory %s\n",h);
                        }

                        //try again
                        if (chdir(h) < 0)
                        {
                                printf("Error changing to directory %s\n",h);
                                exit(1);
                        }
                }
        free(ch_res);

        exit(0);
}

OK, I've found out some more info.

According to the man page for mount_nfs I am already passing the intr flag to allow keyboard interrupts; specifically SIGQUIT and SIGINT.

So, all I need to do is fork, wait and send my process a SIGINT signal.

Do others agree?

This is the answer - it can use a timeout on hard mounted nfs mounted directories.

It uses fork(2), pipe(2), child(2) and kill(2) to create a child that attempts to use the mount.

The parent uses select to set a timeout and listen to a pipe for a successful child response.

Remember to use the intr flag when mounting nfs shares!

Code:

#include        <sys/stat.h>
#include        <signal.h>
#include <stdio.h>
#include <time.h>


void timed_out(){}

int main()
{
        int timeout = 5,check_in = 0;
        int ch_res;
        struct sigaction action;
        FILE *temp_file = NULL;
        int fd,rc,error;
        int fds[2];
        fd_set fdset;
        struct timeval t;
        pid_t child;

        char *h = "/var/tmp/nfs/mount/somewhere/";

        if(pipe(fds) != 0)
        {
                return NULL;
        }
        child = fork();
        if(child == -1)
        {
                printf("Error forking child\n");
                exit(1);
        }

        if( child == 0 )
        {
                char *buf = "ok";
                printf("Child attempting to chdir\n");
                chdir(h);
                printf("Child writing to pipe\n");
                write(fds[1],buf,3);
                close(fds[0]);
                close(fds[1]);
                printf("Child exiting normally\n");
                exit(0);
        }
        else
        {
                t.tv_sec  = timeout;
                t.tv_usec = 0;
                FD_ZERO(&fdset);
                FD_SET(fds[0], &fdset);

                rc = select(fds[0] + 1,&fdset,NULL,NULL,&t);

                if(rc == -1)
                {
                        printf("Error in select\n");
                        close(fds[0]);
                        close(fds[1]);
                        exit(1);
                }
                else if(rc == 0)
                {
                        printf("Timeout - possible nfs error\n");
                        kill(child,SIGINT);
                        close(fds[0]);
                        close(fds[1]);
                        exit(1);
                }
                else if(FD_ISSET(fds[0],&fdset))
                {
                        printf("Got a response, nfs ok\n");
                        //close all stuff
                        close(fds[0]);
                        close(fds[1]);
                }
        }

        ch_res = chdir(h);

        if (ch_res < 0)
        {
                printf("Creating directory %s\n",h);

                if(mkdir(h, 0755))
                {
                        printf("Error making directory %s\n",h);
                        exit(1);
                }
                else
                {
                        printf("Made directory %s\n",h);
                }

                if (chdir(h) < 0)
                {
                        printf("Error changing to directory %s\n",h);
                        exit(1);
                }
        }
        else
        {
                printf("Changed directory successfully %d\n",ch_res);
        }

        exit(0);
}