Re: 2.6.20 kernel hang with USB drive and vfat doing ftruncate

[Kumar Gala]

On Feb 18, 2007, at 10:10 AM, OGAWA Hirofumi wrote:

> Kumar Gala <galak@xxxxxxxxxxxxxxxxxxx> writes:
>
> > I'm seeing an issue with a stock 2.6.20 kernel running on an embedded
> > PPC.  I've got a usb flash drive plugged in and the filesystem on the
> > drive is vfat.  Running with 64M and no swap.
> >
> > If I execute a series of large (100M+) ftruncate() on the disk the
> > kernel will hang and never return.  It seems to be stuck in the idle
> > loop().
> >
> > The following is the test program I'm running:
> >
> > #include <sys/mman.h>
> > #include <sys/types.h>
> > #include <sys/stat.h>
> > #include <fcntl.h>
> > #include <stdio.h>
> > #include <unistd.h>
> > #include <errno.h>
> >
> > void usage (void)
> > {
> >          printf ("truncate_test <filename> <size>\n\n");
> > }
> >
> > int main(int argc, char *argv[])
> > {
> >          int fd, i;
> >          int ret = 0;
> >          unsigned int len;
> >
> >          if (argc != 3) {
> >                  printf("Invalid number of arguments\n\n");
> >                  usage();
> >                  exit(1);
> >          }
> >
> >          fd = open(argv[1], O_CREAT|O_RDWR|O_TRUNC, S_IRWXU);
> >          len = strtoul(argv[2], NULL, 0);
> >
> >          ret = ftruncate(fd, len);
> >
> >          if (ret)
> >                  printf ("ftruncate ret = %d %d\n", ret, errno);
> >
> >          close(fd);
> >
> >          return ret;
> > }
> >
> > I usually run the following twice to get the hang state:
> >
> > time ./trunc_test bar 100000000 &
> > time ./trunc_test baz 100000000 &
> >
> > I was wondering if anyone had any suggestions on what to poke at next
> > to try and figure out what is going on.
>
> Can you check /sys/block/xxx/stat or something to make sure there is
> no outstanding IO request?
>
> It seems to be no response from the lower layer...

Once the system locks up I dont have any ability to do anything.

- k
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