block_dev: use blkdev_issue_zerout for hole punches

This gets us support for non-discard efficient write of zeroes (e.g. NVMe)
and prepares for removing the discard_zeroes_data flag.

Also remove a pointless discard support check, which is done in
blkdev_issue_discard already.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

fs/block_dev.c

@@ -2069,7 +2069,6 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 			     loff_t len)
 {
 	struct block_device *bdev = I_BDEV(bdev_file_inode(file));
-	struct request_queue *q = bdev_get_queue(bdev);
 	struct address_space *mapping;
 	loff_t end = start + len - 1;
 	loff_t isize;
@@ -2108,15 +2107,10 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
 					    GFP_KERNEL, BLKDEV_ZERO_NOUNMAP);
 		break;
 	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
-		/* Only punch if the device can do zeroing discard. */
-		if (!blk_queue_discard(q) || !q->limits.discard_zeroes_data)
-			return -EOPNOTSUPP;
-		error = blkdev_issue_discard(bdev, start >> 9, len >> 9,
-					     GFP_KERNEL, 0);
+		error = blkdev_issue_zeroout(bdev, start >> 9, len >> 9,
+					     GFP_KERNEL, BLKDEV_ZERO_NOFALLBACK);
 		break;
 	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE | FALLOC_FL_NO_HIDE_STALE:
-		if (!blk_queue_discard(q))
-			return -EOPNOTSUPP;
 		error = blkdev_issue_discard(bdev, start >> 9, len >> 9,
 					     GFP_KERNEL, 0);
 		break;