block: bypass the STABLE_WRITES flag for protection information

Currently registering a checksum-enabled (aka PI) integrity profile sets
the QUEUE_FLAG_STABLE_WRITE flag, and unregistering it clears the flag.
This can incorrectly clear the flag when the driver requires stable
writes even without PI, e.g. in case of iSCSI or NVMe/TCP with data
digest enabled.

Fix this by looking at the csum_type directly in bdev_stable_writes and
not setting the queue flag. Also remove the blk_queue_stable_writes
helper as the only user in nvme wants to only look at the actual
QUEUE_FLAG_STABLE_WRITE flag as it inherits the integrity configuration
by other means.

Signed-off-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Martin K. Petersen <[e-mail]>
Reviewed-by: Hannes Reinecke <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jens Axboe <[e-mail]>

block/blk-integrity.c

···
 	bi->tag_size = template->tag_size;
 	bi->pi_offset = template->pi_offset;
 
-	if (bi->csum_type != BLK_INTEGRITY_CSUM_NONE)
-		blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES, disk->queue);
-
 #ifdef CONFIG_BLK_INLINE_ENCRYPTION
 	if (disk->queue->crypto_profile) {
 		pr_warn("blk-integrity: Integrity and hardware inline encryption are not supported together. Disabling hardware inline encryption.\n");
···
 
 	if (!bi->tuple_size)
 		return;
-
-	if (bi->csum_type != BLK_INTEGRITY_CSUM_NONE)
-		blk_queue_flag_clear(QUEUE_FLAG_STABLE_WRITES, disk->queue);
 	memset(bi, 0, sizeof(*bi));
 }
 EXPORT_SYMBOL(blk_integrity_unregister);

drivers/nvme/host/multipath.c

···
 		nvme_mpath_set_live(ns);
 	}
 
-	if (blk_queue_stable_writes(ns->queue) && ns->head->disk)
+	if (test_bit(QUEUE_FLAG_STABLE_WRITES, &ns->queue->queue_flags) &&
+	    ns->head->disk)
 		blk_queue_flag_set(QUEUE_FLAG_STABLE_WRITES,
 				   ns->head->disk->queue);
 #ifdef CONFIG_BLK_DEV_ZONED

include/linux/blkdev.h

···
 #define blk_queue_noxmerges(q)	\
 	test_bit(QUEUE_FLAG_NOXMERGES, &(q)->queue_flags)
 #define blk_queue_nonrot(q)	test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)
-#define blk_queue_stable_writes(q) \
-	test_bit(QUEUE_FLAG_STABLE_WRITES, &(q)->queue_flags)
 #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)	\
···
 
 static inline bool bdev_stable_writes(struct block_device *bdev)
 {
-	return test_bit(QUEUE_FLAG_STABLE_WRITES,
-			&bdev_get_queue(bdev)->queue_flags);
+	struct request_queue *q = bdev_get_queue(bdev);
+
+#ifdef CONFIG_BLK_DEV_INTEGRITY
+	/* BLK_INTEGRITY_CSUM_NONE is not available in blkdev.h */
+	if (q->integrity.csum_type != 0)
+		return true;
+#endif
+	return test_bit(QUEUE_FLAG_STABLE_WRITES, &q->queue_flags);
 }
 
 static inline bool bdev_write_cache(struct block_device *bdev)