On 9/20/21 04:24, Christoph Hellwig wrote:
To prepare for fixing a gendisk shutdown race, open code the
blk_queue_enter logic in bio_queue_enter. This also remove the
^^^^^^
removes
pointless flags translation.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
block/blk-core.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 4c078681f39b8..be7cd1819b605 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -475,18 +475,32 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
static inline int bio_queue_enter(struct bio *bio)
{
struct request_queue *q = bio->bi_bdev->bd_disk->queue;
- bool nowait = bio->bi_opf & REQ_NOWAIT;
- int ret;
- ret = blk_queue_enter(q, nowait ? BLK_MQ_REQ_NOWAIT : 0);
- if (unlikely(ret)) {
- if (nowait && !blk_queue_dying(q))
+ while (!blk_try_enter_queue(q, false)) {
+ if (bio->bi_opf & REQ_NOWAIT) {
bio_wouldblock_error(bio);
- else
+ return -EBUSY;
+ }
+
+ /*
+ * read pair of barrier in blk_freeze_queue_start(), we need to
+ * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and
+ * reading .mq_freeze_depth or queue dying flag, otherwise the
+ * following wait may never return if the two reads are
+ * reordered.
+ */
+ smp_rmb();
+ wait_event(q->mq_freeze_wq,
+ (!q->mq_freeze_depth &&
+ blk_pm_resume_queue(false, q)) ||
+ blk_queue_dying(q));
+ if (blk_queue_dying(q)) {
bio_io_error(bio);
+ return -ENODEV;
+ }
}
- return ret;
+ return 0;
This patch changes the behavior of bio_queue_enter(). I think that
preserving the existing behavior implies testing blk_queue_dying(q)
before checking the REQ_NOWAIT flag.
Thanks,
Bart.
