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SubjectRe: [PATCH] per-backing dev unplugging #2
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On Fri, 2004-03-12 at 15:03, Andrew Morton wrote:
> Chris Mason <mason@suse.com> wrote:
> >
> > During a mixed load test including fsx-linux and a bunch of procs
> > running cp/read/rm loops, I got a null pointer deref with the call
> > trace:
> >
> > __lock_page->sync_page->block_sync_page
> >
> > I don't see how we can trust page->mapping in this path, can't it
> > disappear? If so, it would be a bug without Jens' patch too, just
> > harder to hit.
>
> yup. I wonder why you hit it now.

> This should be sufficient. All callers of lock_page() should have a ref on
> the inode so ->mapping should be stable even if truncate whips the page off
> the inode.
>
I thought the same thing, but blk_run_address_space does an if(mapping)
check already. Looking deeper...

-chris




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