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SubjectRe: Oops in ext3_block_to_path.isra.40+0x26/0x11b
On Fri 16-03-12 10:29:56, Jiri Kosina wrote:
> On Fri, 16 Mar 2012, Jan Kara wrote:
>
> > > CPU is a Core i3 530, on a Gigabyte motherbord, 4 GB RAM. No ECC,
> > > unfortunately, so I can't rule out hardware bit rot. Distribution is
> > > a fairly stock Debian/unstable.
> > Hmm, is any mounting & unmounting happening during your backup? Because
> > the oops happened because sb->s_fs_info was NULL. Dissassembly shows:
> > 16: 48 8b 47 18 mov 0x18(%rdi),%rax
> > store sb->s_blocksize into RAX
> > 1a: 48 8b 8f b0 02 00 00 mov 0x2b0(%rdi),%rcx
> > store sb->s_fs_info into RCX
> > 21: 48 c1 e8 02 shr $0x2,%rax
> > This is division from EXT3_ADDR_PER_BLOCK() - RAX carries 1024 after
> > division so that looks correct.
> >
> > 25: 48 85 db test %rbx,%rbx
> > Now check passed i_block argument.
> >
> > 28: 41 89 c4 mov %eax,%r12d
> > 2b:* 8b b1 94 00 00 00 mov 0x94(%rcx),%esi <-- trapping ins
> > Try to get RCX->s_addr_per_block_bits...
> >
> > sb->s_fs_info is set when a superblock is mounted and cleared when
> > superblock gets unmounted and otherwise it is never changed. So most likely
> > it was some memory corruption clearing that pointer (I wouldn't really
> > suspect HW here).
> >
> > It somewhat looks like the issue described here:
> > http://lkml.indiana.edu/hypermail/linux/kernel/1202.3/00132.html
> >
> > Although there we had f_path.dentry (completely different structure) being
> > NULL. But similarity here is that something stomped NULL over our existing
> > structure.
> >
> > Linus, Jiri, that bug didn't get resolved, did it?
>
> I am not aware of anything, but I have a question -- George, did the
> machine get suspended/resumed before this happened?
And by any chance, do you use i915 driver? Because that one seems to
cause corruption - see: https://lkml.org/lkml/2012/3/9/217. I believe
Jiri's corruption is likely caused by that...

Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


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