[PATCH v4 03/21] iomap: use GFP_NOWAIT when application for iomap_dio_simple allocations

[Joanne Koong <joannelkoong@gmail.com>]

From: Christoph Hellwig <hch@lst.de>

For non-blocking iocbs we should avoid blocking allocation where
possible, so switch to a GFP_NOWAIT allocation here.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/direct-io.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 36c976cf0848..5c28124b9f02 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -986,6 +986,7 @@ static void iomap_dio_simple_end_io(struct bio *bio)
 ssize_t __iomap_dio_read_simple(struct kiocb *iocb, struct iov_iter *iter,
 		struct iomap_iter *iomi)
 {
+	gfp_t gfp = (iomi->flags & IOMAP_NOWAIT) ? GFP_NOWAIT : GFP_KERNEL;
 	struct iomap_dio_simple *sr;
 	unsigned int alignment;
 	struct bio *bio;
@@ -1015,7 +1016,11 @@ ssize_t __iomap_dio_read_simple(struct kiocb *iocb, struct iov_iter *iter,
 
 	bio = bio_alloc_bioset(iomi->iomap.bdev,
 			       bio_iov_vecs_to_alloc(iter, BIO_MAX_VECS),
-			       REQ_OP_READ, GFP_KERNEL, &iomap_dio_simple_pool);
+			       REQ_OP_READ, gfp, &iomap_dio_simple_pool);
+	if (!bio) {
+		ret = -EAGAIN;
+		goto out_dio_end;
+	}
 	sr = container_of(bio, struct iomap_dio_simple, bio);
 	sr->iocb = iocb;
 	sr->dio_flags = 0;
-- 
2.52.0