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-rw-r--r--block/fops.c21
1 files changed, 18 insertions, 3 deletions
diff --git a/block/fops.c b/block/fops.c
index b90742595317..e406aa605327 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -221,6 +221,24 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 			bio_endio(bio);
 			break;
 		}
+		if (iocb->ki_flags & IOCB_NOWAIT) {
+			/*
+			 * This is nonblocking IO, and we need to allocate
+			 * another bio if we have data left to map. As we
+			 * cannot guarantee that one of the sub bios will not
+			 * fail getting issued FOR NOWAIT and as error results
+			 * are coalesced across all of them, be safe and ask for
+			 * a retry of this from blocking context.
+			 */
+			if (unlikely(iov_iter_count(iter))) {
+				bio_release_pages(bio, false);
+				bio_clear_flag(bio, BIO_REFFED);
+				bio_put(bio);
+				blk_finish_plug(&plug);
+				return -EAGAIN;
+			}
+			bio->bi_opf |= REQ_NOWAIT;
+		}
 
 		if (is_read) {
 			if (dio->flags & DIO_SHOULD_DIRTY)
@@ -228,9 +246,6 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 		} else {
 			task_io_account_write(bio->bi_iter.bi_size);
 		}
-		if (iocb->ki_flags & IOCB_NOWAIT)
-			bio->bi_opf |= REQ_NOWAIT;
-
 		dio->size += bio->bi_iter.bi_size;
 		pos += bio->bi_iter.bi_size;