Merge tag 'for-5.11/block-2020-12-14' of git://git.kernel.dk/linux-block

Pull block updates from Jens Axboe:
 "Another series of killing more code than what is being added, again
  thanks to Christoph's relentless cleanups and tech debt tackling.

  This contains:

   - blk-iocost improvements (Baolin Wang)

   - part0 iostat fix (Jeffle Xu)

   - Disable iopoll for split bios (Jeffle Xu)

   - block tracepoint cleanups (Christoph Hellwig)

   - Merging of struct block_device and hd_struct (Christoph Hellwig)

   - Rework/cleanup of how block device sizes are updated (Christoph
     Hellwig)

   - Simplification of gendisk lookup and removal of block device
     aliasing (Christoph Hellwig)

   - Block device ioctl cleanups (Christoph Hellwig)

   - Removal of bdget()/blkdev_get() as exported API (Christoph Hellwig)

   - Disk change rework, avoid ->revalidate_disk() (Christoph Hellwig)

   - sbitmap improvements (Pavel Begunkov)

   - Hybrid polling fix (Pavel Begunkov)

   - bvec iteration improvements (Pavel Begunkov)

   - Zone revalidation fixes (Damien Le Moal)

   - blk-throttle limit fix (Yu Kuai)

   - Various little fixes"

* tag 'for-5.11/block-2020-12-14' of git://git.kernel.dk/linux-block: (126 commits)
  blk-mq: fix msec comment from micro to milli seconds
  blk-mq: update arg in comment of blk_mq_map_queue
  blk-mq: add helper allocating tagset->tags
  Revert "block: Fix a lockdep complaint triggered by request queue flushing"
  nvme-loop: use blk_mq_hctx_set_fq_lock_class to set loop's lock class
  blk-mq: add new API of blk_mq_hctx_set_fq_lock_class
  block: disable iopoll for split bio
  block: Improve blk_revalidate_disk_zones() checks
  sbitmap: simplify wrap check
  sbitmap: replace CAS with atomic and
  sbitmap: remove swap_lock
  sbitmap: optimise sbitmap_deferred_clear()
  blk-mq: skip hybrid polling if iopoll doesn't spin
  blk-iocost: Factor out the base vrate change into a separate function
  blk-iocost: Factor out the active iocgs' state check into a separate function
  blk-iocost: Move the usage ratio calculation to the correct place
  blk-iocost: Remove unnecessary advance declaration
  blk-iocost: Fix some typos in comments
  blktrace: fix up a kerneldoc comment
  block: remove the request_queue to argument request based tracepoints
  ...

1 files changed, 26 insertions, 6 deletions

diff --git a/block/blk-flush.c b/block/blk-flush.c
index fd5cee9f1a3b..76c1624cb06c 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -69,7 +69,6 @@
 #include <linux/blkdev.h>
 #include <linux/gfp.h>
 #include <linux/blk-mq.h>
-#include <linux/lockdep.h>
 
 #include "blk.h"
 #include "blk-mq.h"
@@ -139,7 +138,7 @@ static void blk_flush_queue_rq(struct request *rq, bool add_front)
 
 static void blk_account_io_flush(struct request *rq)
 {
-	struct hd_struct *part = &rq->rq_disk->part0;
+	struct block_device *part = rq->rq_disk->part0;
 
 	part_stat_lock();
 	part_stat_inc(part, ios[STAT_FLUSH]);
@@ -474,9 +473,6 @@ struct blk_flush_queue *blk_alloc_flush_queue(int node, int cmd_size,
 	INIT_LIST_HEAD(&fq->flush_queue[1]);
 	INIT_LIST_HEAD(&fq->flush_data_in_flight);
 
-	lockdep_register_key(&fq->key);
-	lockdep_set_class(&fq->mq_flush_lock, &fq->key);
-
 	return fq;
 
  fail_rq:
@@ -491,7 +487,31 @@ void blk_free_flush_queue(struct blk_flush_queue *fq)
 	if (!fq)
 		return;
 
-	lockdep_unregister_key(&fq->key);
 	kfree(fq->flush_rq);
 	kfree(fq);
 }
+
+/*
+ * Allow driver to set its own lock class to fq->mq_flush_lock for
+ * avoiding lockdep complaint.
+ *
+ * flush_end_io() may be called recursively from some driver, such as
+ * nvme-loop, so lockdep may complain 'possible recursive locking' because
+ * all 'struct blk_flush_queue' instance share same mq_flush_lock lock class
+ * key. We need to assign different lock class for these driver's
+ * fq->mq_flush_lock for avoiding the lockdep warning.
+ *
+ * Use dynamically allocated lock class key for each 'blk_flush_queue'
+ * instance is over-kill, and more worse it introduces horrible boot delay
+ * issue because synchronize_rcu() is implied in lockdep_unregister_key which
+ * is called for each hctx release. SCSI probing may synchronously create and
+ * destroy lots of MQ request_queues for non-existent devices, and some robot
+ * test kernel always enable lockdep option. It is observed that more than half
+ * an hour is taken during SCSI MQ probe with per-fq lock class.
+ */
+void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx,
+		struct lock_class_key *key)
+{
+	lockdep_set_class(&hctx->fq->mq_flush_lock, key);
+}
+EXPORT_SYMBOL_GPL(blk_mq_hctx_set_fq_lock_class);