On Fri, Oct 25, 2024 at 02:36:42PM -0700, Keith Busch wrote:

+static u16 blkdev_write_hint(struct kiocb *iocb, struct block_device *bdev)
+{
+	u16 hint = iocb->ki_write_hint;
+
+	if (!hint)
+		return file_inode(iocb->ki_filp)->i_write_hint;
+
+	if (hint > bdev_max_write_hints(bdev))
+		return file_inode(iocb->ki_filp)->i_write_hint;
+
+	if (bdev_is_partition(bdev) &&
+	    !test_bit(hint - 1, bdev->write_hint_mask))
+		return file_inode(iocb->ki_filp)->i_write_hint;

I would have expected an error when using an invalid stream identifier.

That of course requires telling the application how many are available
through e.g. statx as requested last time.