Re: [PATCH v1 07/12] f2fs: cache: use node cache

[Chao Yu <chao@kernel.org>]

On 8/23/26 20:57, Wenjie Qi wrote:
> Hi Chao,
> 
>> entry = fn->entry;
>> f2fs_cache_get(entry);
>> spin_unlock_irqrestore(&sbi->fsync_node_lock, flags);
>>
>> f2fs_cache_wait_writeback(entry);
> 
> The entry reference keeps the entry allocated, but the waiter does not hold
> the entry lock.  After WRITEBACK is cleared, invalidation can detach the
> entry and set `entry->cache` to NULL.  `f2fs_cache_wait_writeback()` checks
> and uses `entry->cache` through separate accesses.
> 
> Does the reference taken here also guarantee that the parent cache remains
> attached across the wait helper's check and use?

Do you mean race like this?

- f2fs_wait_on_node_caches_writeback
  - f2fs_cache_get
  - f2fs_cache_wait_writeback
   - checked entry->cache, it's valid
						- f2fs_truncate_cache
						 - f2fs_do_truncate_cache
						  - entry->cache = NULL					
   - f2fs_cache_wait_writeback_cond accesses
     invalid entry->cache

Thanks,