On Mon, Mar 15, 2021 at 04:25:32PM +0800, Qu Wenruo wrote:
> 
> 
> On 2021/3/15 下午3:55, Johannes Thumshirn wrote:
> > On 15/03/2021 06:40, Qu Wenruo wrote:
> >> The difference against find_extent_buffer_nospinlock() is:
> >> - Also handles regular sectorsize == PAGE_SIZE case
> >> - No extent buffer refs increase/decrease
> >>    As extent buffer under IO must has non-zero refs.
> >
> > Can these be merged into a single function? The sectorsie == PAGE_SIZE case
> > won't do anything for find_extent_buffer_nospinlock() and the
> > atomic_inc_not_zero(&eb->refs) can be hidden behind a 'if (write)' check.
> 
> That would make the eb refs change too inconsistent.
> 
> But I get your point.
> 
> How about calling find_extent_buffer_nospinlock() and then dec the refs
> manually?

Is this equivalent to this patch? Ie. the atomic_inc_not_zero in
find_extent_buffer_nospinlock happens inside the RCU section, while what
you suggest looks like

find_extent_buffer_nospinlock()
  rcu_lock
  radix_lookup
  rcu_unlock
atomic_inc_not_zero()

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