[PATCH 1/7] io_uring: consider any io_read/write -EAGAIN as final

[Jens Axboe <axboe@kernel.dk>]

If the -EAGAIN happens because of a static condition, then a poll
or later retry won't fix it. We must call it again from blocking
condition. Play it safe and ensure that any -EAGAIN condition from read
or write must retry from async context.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index b43467b3a8dc..e175fed0274a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2255,10 +2255,8 @@ static int io_read(struct io_kiocb *req, struct io_kiocb **nxt,
 	 * If the file doesn't support async, mark it as REQ_F_MUST_PUNT so
 	 * we know to async punt it even if it was opened O_NONBLOCK
 	 */
-	if (force_nonblock && !io_file_supports_async(req->file)) {
-		req->flags |= REQ_F_MUST_PUNT;
+	if (force_nonblock && !io_file_supports_async(req->file))
 		goto copy_iov;
-	}
 
 	iov_count = iov_iter_count(&iter);
 	ret = rw_verify_area(READ, req->file, &kiocb->ki_pos, iov_count);
@@ -2279,6 +2277,8 @@ static int io_read(struct io_kiocb *req, struct io_kiocb **nxt,
 						inline_vecs, &iter);
 			if (ret)
 				goto out_free;
+			/* any defer here is final, must blocking retry */
+			req->flags |= REQ_F_MUST_PUNT;
 			return -EAGAIN;
 		}
 	}
@@ -2344,10 +2344,8 @@ static int io_write(struct io_kiocb *req, struct io_kiocb **nxt,
 	 * If the file doesn't support async, mark it as REQ_F_MUST_PUNT so
 	 * we know to async punt it even if it was opened O_NONBLOCK
 	 */
-	if (force_nonblock && !io_file_supports_async(req->file)) {
-		req->flags |= REQ_F_MUST_PUNT;
+	if (force_nonblock && !io_file_supports_async(req->file))
 		goto copy_iov;
-	}
 
 	/* file path doesn't support NOWAIT for non-direct_IO */
 	if (force_nonblock && !(kiocb->ki_flags & IOCB_DIRECT) &&
@@ -2392,6 +2390,8 @@ static int io_write(struct io_kiocb *req, struct io_kiocb **nxt,
 						inline_vecs, &iter);
 			if (ret)
 				goto out_free;
+			/* any defer here is final, must blocking retry */
+			req->flags |= REQ_F_MUST_PUNT;
 			return -EAGAIN;
 		}
 	}
-- 
2.25.1