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SubjectRe: EXT4 panic at jbd2_journal_put_journal_head() in 3.9+
On Sun, May 12, 2013 at 08:11:59PM -0700, Tony Luck wrote:
>
> My best guess as to why this commit causes problems is that there are places
> where updates to individual fields in this structure used to be independent
> because they were to whole words. Now we have bitfileds there are races
> between access to different fields in the same word.

Yeah, except we access the fields while holding a lock.... wait a
minute. We're using bit_spinlocks().... and am I missing something?

Where are the barrier statements to prevent the CPU or the compiler
from reordering statements around bit_spin_lock()? But if that's the
problem, I would have expected lots of other things to be broken.

- Ted


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