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

[Kumar Gala <galak@kernel.crashing.org>]

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

> Kumar Gala <galak@kernel.crashing.org> 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