On Tue, Mar 26, 2024 at 12:12:03PM +0900, Damien Le Moal wrote: > Nope, we cannot. The reason is that BIO issuing and zone reset/finish can be > concurrently processed and we need to be ready for a user doing really stupid > things like resetting or finishing a zone while BIOs for that zone are being > issued. When zone reset/finish is processed, the plug is removed from the hash > table, but disk_get_zone_wplug_locked() may still get a reference to it because > we do not have the plug locked yet. Hence the flag, to prevent reusing the plug > for the reset/finished zone that was already removed from the hash table. This > is mentioned with a comment in disk_get_zone_wplug_locked(): > > /* > * Check that a BIO completion or a zone reset or finish > * operation has not already flagged the zone write plug for > * freeing and dropped its reference count. In such case, we > * need to get a new plug so start over from the beginning. > */ > > The reference count dropping to 0 will then be the trigger for actually freeing > the plug, after all in-flight or plugged BIOs are completed (most likely failed). Maybe the comment should be expanded even more and move to the definition of the freeing flag?
