loop: use the atomic queue limits update API

Pass the default limits to blk_mq_alloc_disk and then use the
queue_limits_{start,commit}_update API to change the limits in an
atomic way on existing loop gendisks.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20240213073425.1621680-16-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -750,11 +750,11 @@ static void loop_sysfs_exit(struct loop_device *lo)
 				   &loop_attribute_group);
 }
 
-static void loop_config_discard(struct loop_device *lo)
+static void loop_config_discard(struct loop_device *lo,
+		struct queue_limits *lim)
 {
 	struct file *file = lo->lo_backing_file;
 	struct inode *inode = file->f_mapping->host;
-	struct request_queue *q = lo->lo_queue;
 	u32 granularity = 0, max_discard_sectors = 0;
 	struct kstatfs sbuf;
 
@@ -781,12 +781,12 @@ static void loop_config_discard(struct loop_device *lo)
 		granularity = sbuf.f_bsize;
 	}
 
-	blk_queue_max_discard_sectors(q, max_discard_sectors);
-	blk_queue_max_write_zeroes_sectors(q, max_discard_sectors);
+	lim->max_hw_discard_sectors = max_discard_sectors;
+	lim->max_write_zeroes_sectors = max_discard_sectors;
 	if (max_discard_sectors)
-		q->limits.discard_granularity = granularity;
+		lim->discard_granularity = granularity;
 	else
-		q->limits.discard_granularity = 0;
+		lim->discard_granularity = 0;
 }
 
 struct loop_worker {
@@ -975,6 +975,20 @@ loop_set_status_from_info(struct loop_device *lo,
 	return 0;
 }
 
+static int loop_reconfigure_limits(struct loop_device *lo, unsigned short bsize,
+		bool update_discard_settings)
+{
+	struct queue_limits lim;
+
+	lim = queue_limits_start_update(lo->lo_queue);
+	lim.logical_block_size = bsize;
+	lim.physical_block_size = bsize;
+	lim.io_min = bsize;
+	if (update_discard_settings)
+		loop_config_discard(lo, &lim);
+	return queue_limits_commit_update(lo->lo_queue, &lim);
+}
+
 static int loop_configure(struct loop_device *lo, blk_mode_t mode,
 			  struct block_device *bdev,
 			  const struct loop_config *config)
@@ -1072,11 +1086,10 @@ static int loop_configure(struct loop_device *lo, blk_mode_t mode,
 	else
 		bsize = 512;
 
-	blk_queue_logical_block_size(lo->lo_queue, bsize);
-	blk_queue_physical_block_size(lo->lo_queue, bsize);
-	blk_queue_io_min(lo->lo_queue, bsize);
+	error = loop_reconfigure_limits(lo, bsize, true);
+	if (WARN_ON_ONCE(error))
+		goto out_unlock;
 
-	loop_config_discard(lo);
 	loop_update_rotational(lo);
 	loop_update_dio(lo);
 	loop_sysfs_init(lo);
@@ -1143,9 +1156,7 @@ static void __loop_clr_fd(struct loop_device *lo, bool release)
 	lo->lo_offset = 0;
 	lo->lo_sizelimit = 0;
 	memset(lo->lo_file_name, 0, LO_NAME_SIZE);
-	blk_queue_logical_block_size(lo->lo_queue, 512);
-	blk_queue_physical_block_size(lo->lo_queue, 512);
-	blk_queue_io_min(lo->lo_queue, 512);
+	loop_reconfigure_limits(lo, 512, false);
 	invalidate_disk(lo->lo_disk);
 	loop_sysfs_exit(lo);
 	/* let user-space know about this change */
@@ -1477,9 +1488,7 @@ static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
 	invalidate_bdev(lo->lo_device);
 
 	blk_mq_freeze_queue(lo->lo_queue);
-	blk_queue_logical_block_size(lo->lo_queue, arg);
-	blk_queue_physical_block_size(lo->lo_queue, arg);
-	blk_queue_io_min(lo->lo_queue, arg);
+	err = loop_reconfigure_limits(lo, arg, false);
 	loop_update_dio(lo);
 	blk_mq_unfreeze_queue(lo->lo_queue);