io_uring: simplify io_file_supports_nowait()

Make sure that REQ_F_SUPPORT_NOWAIT is always set io_prep_rw(), and so
we can stop caring about setting it down the line simplifying
io_file_supports_nowait().
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/60c8f1f5e2cb45e00f4897b2cec10c5b3669da91.1634425438.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -2764,10 +2764,8 @@ static bool io_bdev_nowait(struct block_device *bdev)
  * any file. For now, just ensure that anything potentially problematic is done
  * inline.
  */
-static bool __io_file_supports_nowait(struct file *file)
+static bool __io_file_supports_nowait(struct file *file, umode_t mode)
 {
-	umode_t mode = file_inode(file)->i_mode;
-
 	if (S_ISBLK(mode)) {
 		if (IS_ENABLED(CONFIG_BLOCK) &&
 		    io_bdev_nowait(I_BDEV(file->f_mapping->host)))
@@ -2790,11 +2788,26 @@ static bool __io_file_supports_nowait(struct file *file)
 	return file->f_mode & FMODE_NOWAIT;
 }
 
+/*
+ * If we tracked the file through the SCM inflight mechanism, we could support
+ * any file. For now, just ensure that anything potentially problematic is done
+ * inline.
+ */
+static unsigned int io_file_get_flags(struct file *file)
+{
+	umode_t mode = file_inode(file)->i_mode;
+	unsigned int res = 0;
+
+	if (S_ISREG(mode))
+		res |= FFS_ISREG;
+	if (__io_file_supports_nowait(file, mode))
+		res |= FFS_NOWAIT;
+	return res;
+}
+
 static inline bool io_file_supports_nowait(struct io_kiocb *req)
 {
-	if (likely(req->flags & REQ_F_SUPPORT_NOWAIT))
-		return true;
-	return __io_file_supports_nowait(req->file);
+	return req->flags & REQ_F_SUPPORT_NOWAIT;
 }
 
 static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
@@ -2806,8 +2819,8 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 	unsigned ioprio;
 	int ret;
 
-	if (!io_req_ffs_set(req) && S_ISREG(file_inode(file)->i_mode))
-		req->flags |= REQ_F_ISREG;
+	if (!io_req_ffs_set(req))
+		req->flags |= io_file_get_flags(file) << REQ_F_SUPPORT_NOWAIT_BIT;
 
 	kiocb->ki_pos = READ_ONCE(sqe->off);
 	if (kiocb->ki_pos == -1 && !(file->f_mode & FMODE_STREAM)) {
@@ -6761,10 +6774,7 @@ static void io_fixed_file_set(struct io_fixed_file *file_slot, struct file *file
 {
 	unsigned long file_ptr = (unsigned long) file;
 
-	if (__io_file_supports_nowait(file))
-		file_ptr |= FFS_NOWAIT;
-	if (S_ISREG(file_inode(file)->i_mode))
-		file_ptr |= FFS_ISREG;
+	file_ptr |= io_file_get_flags(file);
 	file_slot->file_ptr = file_ptr;
 }