Re: BUG in ext2

[Andrew Morton]

Andreas Dilger wrote:
> 
> Andrew Morton writes:
> > test6-pre2, x86, UP, gcc 2.7.2.3.
> >
> > I'm getting a 100% reproducible assertion failure at balloc.c:558:
> >
> >                  * way it could happen, thus the BUG().
> >                  */
> >                 if (*prealloc_count)
> >                         BUG();
> >                 *prealloc_count = 0;
> >                 *prealloc_block = next_block;
> >                 /* Writer: end */
> >
> > This is happening when running mmap002.  I've put a gdb backtrace up at
> > http://www.uow.edu.au/~andrewm/ext2.txt
> 
> Unfortunately, the whole ext2 block allocation code was re-written
> recently by Al Viro for test6-pre1, and it looks like it has bugs (see
> also thread <test6-pre2 loop in ext2_get_block>)...

I suspect this problem is a simple one.  Replacing the BUG() with a
printk(*prealloc_count) reveals that it is non-zero about six times during an
mmap002 run.  Values vary from 1 to 7.  No problems observed from this
workaround.