Re: raspberry pi panic 7.0_BETA after install fs resize

[Maxime Villard <max%M00nBSD.net@localhost>]

Le 06/11/2014 08:28, Michael van Elst a écrit :
> petri.laakso%asd.fi@localhost (Petri Laakso) writes:
>
>
> > On Fri, 31 Oct 2014, Maxime Villard wrote:
> > > That's KMEM_SIZE. Great.
> > > It means that it caught a memory corruption somewhere.
> > > That being said, I don't think I can help without a trace...
>
> > Here's backtrace and steps how I ended up with panic. This was in
> > single user mode after fresh 7.0_BETA install (sources from last night)
>
> > http://www.asd.fi/~petri/tmp/rpi_bt.jpg
>
> > Petri
>
> malloc considered useful:
>
> allocation in ffs_mountfs:
>          bsize = fs->fs_cssize;
>          if (fs->fs_contigsumsize > 0)
>                  bsize += fs->fs_ncg * sizeof(int32_t);
>          bsize += fs->fs_ncg * sizeof(*fs->fs_contigdirs);
>          allocsbsize = bsize;
>          space = kmem_alloc((u_long)allocsbsize, KM_SLEEP);
>          fs->fs_csp = space;
>
> deallocation in ffs_unmount:
>          bsize = fs->fs_cssize;
>          if (fs->fs_contigsumsize > 0)
>                  bsize += fs->fs_ncg * sizeof(int32_t);
>          bsize += fs->fs_ncg * sizeof(*fs->fs_contigdirs);
>          kmem_free(fs->fs_csp, bsize);
>
>
> allocsbsize only exists to handle some error paths, but since
> it is not stored globally, the value is recalculated, assuming
> that the underlying values do not change.
>
> Apparently that's not true after the resize of the filesystem.

Yes. That's similar to the mail I sent some days ago on tech-kern@:

http://mail-index.netbsd.org/tech-kern/2014/10/27/msg017874.html

I think we should implement a set of kmem_vXX functions, which
don't need a size argument to free:
	void *kmem_valloc(size_t size)
	void kmem_vfree(void *ptr)

Such an allocator would be very useful; not only in ffs, but in
many other places where strange hacks in structures are necessary
to hold the allocated size.

It is easy to implement, and kmem_valloc(0) wouldn't panic the
system - contrary to kmem_alloc().

> The other question is, does anyone use the fs->fs_csp buffer
> and assumes it is calculated for the updated values before it
> is freed?