[PATCH 4/6] block: freeze queue for updating QUEUE_FLAG_NONROT

[Ming Lei <ming.lei@redhat.com>]

We will read the NONROT flag for bypassing scsi->device_busy in SCSI
IO path, so have to freeze queue when updating this flag.

Cc: Sathya Prakash <sathya.prakash@broadcom.com>
Cc: Chaitra P B <chaitra.basappa@broadcom.com>
Cc: Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Sumit Saxena <sumit.saxena@broadcom.com>
Cc: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>,
Cc: Hannes Reinecke <hare@suse.de>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-sysfs.c | 14 +++++++++++++-
 drivers/scsi/sd.c |  4 ++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index fca9b158f4a0..9cc0dd5f88a1 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -281,6 +281,18 @@ QUEUE_SYSFS_BIT_FNS(random, ADD_RANDOM, 0);
 QUEUE_SYSFS_BIT_FNS(iostats, IO_STAT, 0);
 #undef QUEUE_SYSFS_BIT_FNS
 
+static ssize_t queue_store_nonrot_freeze(struct request_queue *q,
+		const char *page, size_t count)
+{
+	size_t ret;
+
+	blk_mq_freeze_queue(q);
+	ret = queue_store_nonrot(q, page, count);
+	blk_mq_unfreeze_queue(q);
+
+	return ret;
+}
+
 static ssize_t queue_zoned_show(struct request_queue *q, char *page)
 {
 	switch (blk_queue_zoned_model(q)) {
@@ -642,7 +654,7 @@ static struct queue_sysfs_entry queue_write_zeroes_max_entry = {
 static struct queue_sysfs_entry queue_nonrot_entry = {
 	.attr = {.name = "rotational", .mode = 0644 },
 	.show = queue_show_nonrot,
-	.store = queue_store_nonrot,
+	.store = queue_store_nonrot_freeze,
 };
 
 static struct queue_sysfs_entry queue_zoned_entry = {
diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index f401ba96dcfd..349c944b29a3 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -2935,7 +2935,9 @@ static void sd_read_block_characteristics(struct scsi_disk *sdkp)
 	rot = get_unaligned_be16(&buffer[4]);
 
 	if (rot == 1) {
+		blk_mq_freeze_queue(q);
 		blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
+		blk_mq_unfreeze_queue(q);
 		blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, q);
 	}
 
@@ -3131,7 +3133,9 @@ static int sd_revalidate_disk(struct gendisk *disk)
 		 * cause this to be updated correctly and any device which
 		 * doesn't support it should be treated as rotational.
 		 */
+		blk_mq_freeze_queue(q);
 		blk_queue_flag_clear(QUEUE_FLAG_NONROT, q);
+		blk_mq_unfreeze_queue(q);
 		blk_queue_flag_set(QUEUE_FLAG_ADD_RANDOM, q);
 
 		if (scsi_device_supports_vpd(sdp)) {
-- 
2.20.1