iomap: don't try to poll multi-bio I/Os in __iomap_dio_rw

If an iocb is split into multiple bios we can't poll for both.  So don't
bother to even try to poll in that case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-4-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/iomap/direct-io.c

@@ -282,6 +282,13 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
 	if (!iov_iter_count(dio->submit.iter))
 		goto out;
 
+	/*
+	 * We can only poll for single bio I/Os.
+	 */
+	if (need_zeroout ||
+	    ((dio->flags & IOMAP_DIO_WRITE) && pos >= i_size_read(inode)))
+		dio->iocb->ki_flags &= ~IOCB_HIPRI;
+
 	if (need_zeroout) {
 		/* zero out from the start of the block to the write offset */
 		pad = pos & (fs_block_size - 1);
@@ -339,6 +346,11 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter,
 
 		nr_pages = bio_iov_vecs_to_alloc(dio->submit.iter,
 						 BIO_MAX_VECS);
+		/*
+		 * We can only poll for single bio I/Os.
+		 */
+		if (nr_pages)
+			dio->iocb->ki_flags &= ~IOCB_HIPRI;
 		iomap_dio_submit_bio(iter, dio, bio, pos);
 		pos += n;
 	} while (nr_pages);
@@ -565,8 +577,15 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 	inode_dio_begin(inode);
 
 	blk_start_plug(&plug);
-	while ((ret = iomap_iter(&iomi, ops)) > 0)
+	while ((ret = iomap_iter(&iomi, ops)) > 0) {
 		iomi.processed = iomap_dio_iter(&iomi, dio);
+
+		/*
+		 * We can only poll for single bio I/Os.
+		 */
+		iocb->ki_flags &= ~IOCB_HIPRI;
+	}
+
 	blk_finish_plug(&plug);
 
 	/*