block: keep q_usage_counter in atomic mode after del_gendisk

Don't switch back to percpu mode to avoid the double RCU grace period
when tearing down SCSI devices.  After removing the disk only passthrough
commands can be send anyway.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20210929071241.934472-6-hch@lst.de
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 108a352051be5fea9c7a5c132576844c3f3ee8a7..bc026372de4394eb003fde3c1b0de7a79df1fdc0 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -188,9 +188,11 @@ void blk_mq_freeze_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);
 
-void blk_mq_unfreeze_queue(struct request_queue *q)
+void __blk_mq_unfreeze_queue(struct request_queue *q, bool force_atomic)
 {
        mutex_lock(&q->mq_freeze_lock);
+       if (force_atomic)
+               q->q_usage_counter.data->force_atomic = true;
        q->mq_freeze_depth--;
        WARN_ON_ONCE(q->mq_freeze_depth < 0);
        if (!q->mq_freeze_depth) {
@@ -199,6 +201,11 @@ void blk_mq_unfreeze_queue(struct request_queue *q)
        }
        mutex_unlock(&q->mq_freeze_lock);
 }
+
+void blk_mq_unfreeze_queue(struct request_queue *q)
+{
+       __blk_mq_unfreeze_queue(q, false);
+}
 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
 
 /*

diff --git a/block/blk.h b/block/blk.h
index e2ed2257709ae4cb92efb710c8241dd27fd411ea..6c3c00a8fe19d3f4f926d3deb9f26d63577c6f3c 100644 (file)
--- a/block/blk.h
+++ b/block/blk.h
@@ -51,6 +51,7 @@ struct blk_flush_queue *blk_alloc_flush_queue(int node, int cmd_size,
 void blk_free_flush_queue(struct blk_flush_queue *q);
 
 void blk_freeze_queue(struct request_queue *q);
+void __blk_mq_unfreeze_queue(struct request_queue *q, bool force_atomic);
 void blk_queue_start_drain(struct request_queue *q);
 
 #define BIO_INLINE_VECS 4

diff --git a/block/genhd.c b/block/genhd.c
index 1fe816be9bcdbba63b1d9ac9946b8f02a270ce40..7a766cc613c76795a3123551ef8aa859edfacc52 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -596,7 +596,8 @@ void del_gendisk(struct gendisk *disk)
        /*
         * Allow using passthrough request again after the queue is torn down.
         */
-       blk_mq_unfreeze_queue(q);
+       blk_queue_flag_clear(QUEUE_FLAG_INIT_DONE, q);
+       __blk_mq_unfreeze_queue(q, true);
 
        if (!(disk->flags & GENHD_FL_HIDDEN)) {
                sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");