Re: [PATCH v4 08/15] btrfs: Stop using call_rcu for device freeing

[Nikolay Borisov]

On 1.04.19 г. 20:07 ч., David Sterba wrote:
> On Wed, Mar 27, 2019 at 02:24:11PM +0200, Nikolay Borisov wrote:
>> btrfs_device structs are freed from RCU context since device iteration
>> is protected by RCU. Currently this is achieved by using call_rcu since
>> no blocking functions are called within btrfs_free_device. Future
>> refactoring of pending/pinned chunks will require calling sleeping
>> functions. This patch is in preparation for these changes by simply
>> switching from RCU callbacks to explicit calls of synchronize_rcu and
>> calling btrfs_free_device directly.
> 
> A paragraph why this transition is correct would be good. It looks
> correct to me, so this is a matter of documentation.
> 

Well call_rcu and synchronize_rcu() are functionally equivalent in that
they run the code that follows them after a grace period has expired.