On Mon, Mar 15, 2021 at 04:25:32PM +0800, Qu Wenruo wrote:

On 2021/3/15 下午3:55, Johannes Thumshirn wrote:

quoted

On 15/03/2021 06:40, Qu Wenruo wrote:

quoted

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()