block: move the add_random flag to queue_limits

Move the add_random flag into the queue_limits feature field so that it
can be set atomically with the queue frozen.

Note that this also removes code from dm to clear the flag based on
the underlying devices, which can't be reached as dm devices will
always start out without the flag set.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20240617060532.127975-16-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

block/blk-mq-debugfs.c

@@ -86,7 +86,6 @@ static const char *const blk_queue_flag_name[] = {
 	QUEUE_FLAG_NAME(FAIL_IO),
 	QUEUE_FLAG_NAME(IO_STAT),
 	QUEUE_FLAG_NAME(NOXMERGES),
-	QUEUE_FLAG_NAME(ADD_RANDOM),
 	QUEUE_FLAG_NAME(SYNCHRONOUS),
 	QUEUE_FLAG_NAME(SAME_FORCE),
 	QUEUE_FLAG_NAME(INIT_DONE),

block/blk-sysfs.c

@@ -323,7 +323,7 @@ queue_##name##_store(struct request_queue *q, const char *page, size_t count) \
 }
 
 QUEUE_SYSFS_FEATURE(rotational, BLK_FEAT_ROTATIONAL)
-QUEUE_SYSFS_BIT_FNS(random, ADD_RANDOM, 0);
+QUEUE_SYSFS_FEATURE(add_random, BLK_FEAT_ADD_RANDOM)
 QUEUE_SYSFS_BIT_FNS(iostats, IO_STAT, 0);
 QUEUE_SYSFS_BIT_FNS(stable_writes, STABLE_WRITES, 0);
 #undef QUEUE_SYSFS_BIT_FNS
@@ -561,7 +561,7 @@ static struct queue_sysfs_entry queue_hw_sector_size_entry = {
 
 QUEUE_RW_ENTRY(queue_rotational, "rotational");
 QUEUE_RW_ENTRY(queue_iostats, "iostats");
-QUEUE_RW_ENTRY(queue_random, "add_random");
+QUEUE_RW_ENTRY(queue_add_random, "add_random");
 QUEUE_RW_ENTRY(queue_stable_writes, "stable_writes");
 
 #ifdef CONFIG_BLK_WBT
@@ -665,7 +665,7 @@ static struct attribute *queue_attrs[] = {
 	&queue_nomerges_entry.attr,
 	&queue_iostats_entry.attr,
 	&queue_stable_writes_entry.attr,
-	&queue_random_entry.attr,
+	&queue_add_random_entry.attr,
 	&queue_poll_entry.attr,
 	&queue_wc_entry.attr,
 	&queue_fua_entry.attr,

drivers/block/mtip32xx/mtip32xx.c

@@ -3485,7 +3485,6 @@ static int mtip_block_initialize(struct driver_data *dd)
 		goto start_service_thread;
 
 	/* Set device limits. */
-	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, dd->queue);
 	dma_set_max_seg_size(&dd->pdev->dev, 0x400000);
 
 	/* Set the capacity of the device in 512 byte sectors. */

drivers/md/dm-table.c

@@ -1716,14 +1716,6 @@ static int device_dax_write_cache_enabled(struct dm_target *ti,
 	return false;
 }
 
-static int device_is_not_random(struct dm_target *ti, struct dm_dev *dev,
-			     sector_t start, sector_t len, void *data)
-{
-	struct request_queue *q = bdev_get_queue(dev->bdev);
-
-	return !blk_queue_add_random(q);
-}
-
 static int device_not_write_zeroes_capable(struct dm_target *ti, struct dm_dev *dev,
 					   sector_t start, sector_t len, void *data)
 {
@@ -1876,16 +1868,6 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	else
 		blk_queue_flag_clear(QUEUE_FLAG_STABLE_WRITES, q);
 
-	/*
-	 * Determine whether or not this queue's I/O timings contribute
-	 * to the entropy pool, Only request-based targets use this.
-	 * Clear QUEUE_FLAG_ADD_RANDOM if any underlying device does not
-	 * have it set.
-	 */
-	if (blk_queue_add_random(q) &&
-	    dm_table_any_dev_attr(t, device_is_not_random, NULL))
-		blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, q);
-
 	/*
 	 * For a zoned target, setup the zones related queue attributes
 	 * and resources necessary for zone append emulation if necessary.

drivers/mmc/core/queue.c

@@ -387,8 +387,6 @@ static struct gendisk *mmc_alloc_disk(struct mmc_queue *mq,
 		blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, mq->queue);
 	blk_queue_rq_timeout(mq->queue, 60 * HZ);
 
-	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, mq->queue);
-
 	dma_set_max_seg_size(mmc_dev(host), queue_max_segment_size(mq->queue));
 
 	INIT_WORK(&mq->recovery_work, mmc_mq_recovery_handler);

drivers/mtd/mtd_blkdevs.c

@@ -374,9 +374,6 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
 	/* Create the request queue */
 	spin_lock_init(&new->queue_lock);
 	INIT_LIST_HEAD(&new->rq_list);
-
-	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, new->rq);
-
 	gd->queue = new->rq;
 
 	if (new->readonly)

drivers/s390/block/scm_blk.c

@@ -439,7 +439,6 @@ int scm_blk_dev_setup(struct scm_blk_dev *bdev, struct scm_device *scmdev)
 		.logical_block_size	= 1 << 12,
 	};
 	unsigned int devindex;
-	struct request_queue *rq;
 	int len, ret;
 
 	lim.max_segments = min(scmdev->nr_max_block,
@@ -474,9 +473,6 @@ int scm_blk_dev_setup(struct scm_blk_dev *bdev, struct scm_device *scmdev)
 		ret = PTR_ERR(bdev->gendisk);
 		goto out_tag;
 	}
-	rq = bdev->rq = bdev->gendisk->queue;
-	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, rq);
-
 	bdev->gendisk->private_data = scmdev;
 	bdev->gendisk->fops = &scm_blk_devops;
 	bdev->gendisk->major = scm_major;

drivers/scsi/scsi_lib.c

@@ -631,8 +631,7 @@ static bool scsi_end_request(struct request *req, blk_status_t error,
 	if (blk_update_request(req, error, bytes))
 		return true;
 
-	// XXX:
-	if (blk_queue_add_random(q))
+	if (q->limits.features & BLK_FEAT_ADD_RANDOM)
 		add_disk_randomness(req->q->disk);
 
 	WARN_ON_ONCE(!blk_rq_is_passthrough(req) &&

drivers/scsi/sd.c

@@ -3301,7 +3301,6 @@ static void sd_read_block_limits_ext(struct scsi_disk *sdkp)
 static void sd_read_block_characteristics(struct scsi_disk *sdkp,
 		struct queue_limits *lim)
 {
-	struct request_queue *q = sdkp->disk->queue;
 	struct scsi_vpd *vpd;
 	u16 rot;
 
@@ -3317,10 +3316,8 @@ static void sd_read_block_characteristics(struct scsi_disk *sdkp,
 	sdkp->zoned = (vpd->data[8] >> 4) & 3;
 	rcu_read_unlock();
 
-	if (rot == 1) {
-		lim->features &= ~BLK_FEAT_ROTATIONAL;
-		blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, q);
-	}
+	if (rot == 1)
+		lim->features &= ~(BLK_FEAT_ROTATIONAL | BLK_FEAT_ADD_RANDOM);
 
 	if (!sdkp->first_scan)
 		return;
@@ -3599,7 +3596,6 @@ static int sd_revalidate_disk(struct gendisk *disk)
 {
 	struct scsi_disk *sdkp = scsi_disk(disk);
 	struct scsi_device *sdp = sdkp->device;
-	struct request_queue *q = sdkp->disk->queue;
 	sector_t old_capacity = sdkp->capacity;
 	struct queue_limits lim;
 	unsigned char *buffer;
@@ -3646,8 +3642,7 @@ 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.
 		 */
-		lim.features |= BLK_FEAT_ROTATIONAL;
-		blk_queue_flag_set(QUEUE_FLAG_ADD_RANDOM, q);
+		lim.features |= (BLK_FEAT_ROTATIONAL | BLK_FEAT_ADD_RANDOM);
 
 		if (scsi_device_supports_vpd(sdp)) {
 			sd_read_block_provisioning(sdkp);

include/linux/blkdev.h

@@ -292,6 +292,9 @@ enum {
 
 	/* rotational device (hard drive or floppy) */
 	BLK_FEAT_ROTATIONAL			= (1u << 2),
+
+	/* contributes to the random number pool */
+	BLK_FEAT_ADD_RANDOM			= (1u << 3),
 };
 
 /*
@@ -557,7 +560,6 @@ struct request_queue {
 #define QUEUE_FLAG_FAIL_IO	5	/* fake timeout */
 #define QUEUE_FLAG_IO_STAT	7	/* do disk/partitions IO accounting */
 #define QUEUE_FLAG_NOXMERGES	9	/* No extended merges */
-#define QUEUE_FLAG_ADD_RANDOM	10	/* Contributes to random pool */
 #define QUEUE_FLAG_SYNCHRONOUS	11	/* always completes in submit context */
 #define QUEUE_FLAG_SAME_FORCE	12	/* force complete on same CPU */
 #define QUEUE_FLAG_INIT_DONE	14	/* queue is initialized */
@@ -591,7 +593,6 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q);
 	test_bit(QUEUE_FLAG_NOXMERGES, &(q)->queue_flags)
 #define blk_queue_nonrot(q)	((q)->limits.features & BLK_FEAT_ROTATIONAL)
 #define blk_queue_io_stat(q)	test_bit(QUEUE_FLAG_IO_STAT, &(q)->queue_flags)
-#define blk_queue_add_random(q)	test_bit(QUEUE_FLAG_ADD_RANDOM, &(q)->queue_flags)
 #define blk_queue_zone_resetall(q)	\
 	test_bit(QUEUE_FLAG_ZONE_RESETALL, &(q)->queue_flags)
 #define blk_queue_dax(q)	test_bit(QUEUE_FLAG_DAX, &(q)->queue_flags)