On Wed, May 07, 2025 at 10:28:24PM +0800, Ming Lei wrote: > On Wed, May 07, 2025 at 03:53:49PM +0200, Christoph Hellwig wrote: > > On Wed, May 07, 2025 at 08:04:02PM +0800, Ming Lei wrote: > > > blk_mq_freeze_queue() can't be called on quiesced queue, otherwise it may > > > never return if there is any queued requests. > > > > > > Fix it by moving queue quiesce int elevator_change() by adding one flag to > > > 'struct elv_change_ctx' for controlling this behavior. > > > > Why do we even need to quiesce the queue here, and not anywhere else? > > Quiesce is for draining the in-progress critical area, which can't be > covered by queue freeze. Typically, all requests are freed, the run queue > activity isn't finished yet, so schedule data can be touched by the un-finished > code path. > > We did fix this kind of bugs by queue quiesce several times. For example: 24f5a90f0d13 blk-mq: quiesce queue during switching io sched and updating nr_requests c2856ae2f315 blk-mq: quiesce queue before freeing queue Ming
