block: move the synchronous flag to queue_limits

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

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/20240617060532.127975-19-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

block/blk-mq-debugfs.c

@@ -85,7 +85,6 @@ static const char *const blk_queue_flag_name[] = {
 	QUEUE_FLAG_NAME(SAME_COMP),
 	QUEUE_FLAG_NAME(FAIL_IO),
 	QUEUE_FLAG_NAME(NOXMERGES),
-	QUEUE_FLAG_NAME(SYNCHRONOUS),
 	QUEUE_FLAG_NAME(SAME_FORCE),
 	QUEUE_FLAG_NAME(INIT_DONE),
 	QUEUE_FLAG_NAME(POLL),

drivers/block/brd.c

@@ -335,6 +335,7 @@ static int brd_alloc(int i)
 		.max_hw_discard_sectors	= UINT_MAX,
 		.max_discard_segments	= 1,
 		.discard_granularity	= PAGE_SIZE,
+		.features		= BLK_FEAT_SYNCHRONOUS,
 	};
 
 	list_for_each_entry(brd, &brd_devices, brd_list)
@@ -366,7 +367,6 @@ static int brd_alloc(int i)
 	strscpy(disk->disk_name, buf, DISK_NAME_LEN);
 	set_capacity(disk, rd_size * 2);
 
-	blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, disk->queue);
 	blk_queue_flag_set(QUEUE_FLAG_NOWAIT, disk->queue);
 	err = add_disk(disk);
 	if (err)

drivers/block/zram/zram_drv.c

@@ -2208,7 +2208,8 @@ static int zram_add(void)
 #if ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE
 		.max_write_zeroes_sectors	= UINT_MAX,
 #endif
-		.features			= BLK_FEAT_STABLE_WRITES,
+		.features			= BLK_FEAT_STABLE_WRITES |
+						  BLK_FEAT_SYNCHRONOUS,
 	};
 	struct zram *zram;
 	int ret, device_id;
@@ -2246,7 +2247,6 @@ static int zram_add(void)
 
 	/* Actual capacity set using sysfs (/sys/block/zram<id>/disksize */
 	set_capacity(zram->disk, 0);
-	blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, zram->disk->queue);
 	ret = device_add_disk(NULL, zram->disk, zram_disk_groups);
 	if (ret)
 		goto out_cleanup_disk;

drivers/nvdimm/btt.c

@@ -1501,6 +1501,7 @@ static int btt_blk_init(struct btt *btt)
 		.logical_block_size	= btt->sector_size,
 		.max_hw_sectors		= UINT_MAX,
 		.max_integrity_segments	= 1,
+		.features		= BLK_FEAT_SYNCHRONOUS,
 	};
 	int rc;
 
@@ -1518,8 +1519,6 @@ static int btt_blk_init(struct btt *btt)
 	btt->btt_disk->fops = &btt_fops;
 	btt->btt_disk->private_data = btt;
 
-	blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, btt->btt_disk->queue);
-
 	set_capacity(btt->btt_disk, btt->nlba * btt->sector_size >> 9);
 	rc = device_add_disk(&btt->nd_btt->dev, btt->btt_disk, NULL);
 	if (rc)

drivers/nvdimm/pmem.c

@@ -455,7 +455,8 @@ static int pmem_attach_disk(struct device *dev,
 		.logical_block_size	= pmem_sector_size(ndns),
 		.physical_block_size	= PAGE_SIZE,
 		.max_hw_sectors		= UINT_MAX,
-		.features		= BLK_FEAT_WRITE_CACHE,
+		.features		= BLK_FEAT_WRITE_CACHE |
+					  BLK_FEAT_SYNCHRONOUS,
 	};
 	int nid = dev_to_node(dev), fua;
 	struct resource *res = &nsio->res;
@@ -546,7 +547,6 @@ static int pmem_attach_disk(struct device *dev,
 	}
 	pmem->virt_addr = addr;
 
-	blk_queue_flag_set(QUEUE_FLAG_SYNCHRONOUS, q);
 	if (pmem->pfn_flags & PFN_MAP)
 		blk_queue_flag_set(QUEUE_FLAG_DAX, q);
 

include/linux/blkdev.h

@@ -301,6 +301,9 @@ enum {
 
 	/* don't modify data until writeback is done */
 	BLK_FEAT_STABLE_WRITES			= (1u << 5),
+
+	/* always completes in submit context */
+	BLK_FEAT_SYNCHRONOUS			= (1u << 6),
 };
 
 /*
@@ -566,7 +569,6 @@ struct request_queue {
 #define QUEUE_FLAG_SAME_COMP	4	/* complete on same CPU-group */
 #define QUEUE_FLAG_FAIL_IO	5	/* fake timeout */
 #define QUEUE_FLAG_NOXMERGES	9	/* No extended merges */
-#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 */
 #define QUEUE_FLAG_POLL		16	/* IO polling enabled if set */
@@ -1315,8 +1317,7 @@ static inline bool bdev_nonrot(struct block_device *bdev)
 
 static inline bool bdev_synchronous(struct block_device *bdev)
 {
-	return test_bit(QUEUE_FLAG_SYNCHRONOUS,
-			&bdev_get_queue(bdev)->queue_flags);
+	return bdev->bd_disk->queue->limits.features & BLK_FEAT_SYNCHRONOUS;
 }
 
 static inline bool bdev_stable_writes(struct block_device *bdev)