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ublk_drv: check 'current' instead of 'ubq_daemon'

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This check is not atomic. So with recovery feature, ubq_daemon may be
modified simultaneously by recovery task. Instead, check 'current' is
safe here because 'current' never changes.

Also add comment explaining this check, which is really important for
understanding recovery feature.

Signed-off-by: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220923153919.44078-2-ZiyangZhang@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
ZiyangZhang 2022-09-23 23:39:13 +08:00 committed by Jens Axboe
parent 4324796ed0
commit ae3f719300
1 changed files with 10 additions and 2 deletions
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12
drivers/block/ublk_drv.c
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@ -645,14 +645,22 @@ static inline void __ublk_rq_task_work(struct request *req)
struct ublk_device *ub = ubq->dev;
int tag = req->tag;
struct ublk_io *io = &ubq->ios[tag];
bool task_exiting = current != ubq->ubq_daemon || ubq_daemon_is_dying(ubq);
unsigned int mapped_bytes;
pr_devel("%s: complete: op %d, qid %d tag %d io_flags %x addr %llx\n",
__func__, io->cmd->cmd_op, ubq->q_id, req->tag, io->flags,
ublk_get_iod(ubq, req->tag)->addr);
if (unlikely(task_exiting)) {
/*
* Task is exiting if either:
*
* (1) current != ubq_daemon.
* io_uring_cmd_complete_in_task() tries to run task_work
* in a workqueue if ubq_daemon(cmd's task) is PF_EXITING.
*
* (2) current->flags & PF_EXITING.
*/
if (unlikely(current != ubq->ubq_daemon || current->flags & PF_EXITING)) {
blk_mq_end_request(req, BLK_STS_IOERR);
mod_delayed_work(system_wq, &ub->monitor_work, 0);
return;