fs: remove aio_run_iocb

Pass the ABI iocb structure to aio_setup_rw and let it handle the
non-vectored I/O case as well.  With that and a new helper for the AIO
return value handling we can now define new aio_read and aio_write
helpers that implement reads and writes in a self-contained way without
duplicating too much code.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/aio.c

@@ -1392,110 +1392,100 @@ SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
 	return -EINVAL;
 }
 
-typedef ssize_t (rw_iter_op)(struct kiocb *, struct iov_iter *);
-
-static int aio_setup_vectored_rw(int rw, char __user *buf, size_t len,
-				 struct iovec **iovec,
-				 bool compat,
-				 struct iov_iter *iter)
+static int aio_setup_rw(int rw, struct iocb *iocb, struct iovec **iovec,
+		bool vectored, bool compat, struct iov_iter *iter)
 {
+	void __user *buf = (void __user *)(uintptr_t)iocb->aio_buf;
+	size_t len = iocb->aio_nbytes;
+
+	if (!vectored) {
+		ssize_t ret = import_single_range(rw, buf, len, *iovec, iter);
+		*iovec = NULL;
+		return ret;
+	}
 #ifdef CONFIG_COMPAT
 	if (compat)
-		return compat_import_iovec(rw,
-				(struct compat_iovec __user *)buf,
-				len, UIO_FASTIOV, iovec, iter);
+		return compat_import_iovec(rw, buf, len, UIO_FASTIOV, iovec,
+				iter);
 #endif
-	return import_iovec(rw, (struct iovec __user *)buf,
-				len, UIO_FASTIOV, iovec, iter);
+	return import_iovec(rw, buf, len, UIO_FASTIOV, iovec, iter);
 }
 
-/*
- * aio_run_iocb:
- *	Performs the initial checks and io submission.
+static inline ssize_t aio_ret(struct kiocb *req, ssize_t ret)
+{
+	switch (ret) {
+	case -EIOCBQUEUED:
+		return ret;
+	case -ERESTARTSYS:
+	case -ERESTARTNOINTR:
+	case -ERESTARTNOHAND:
+	case -ERESTART_RESTARTBLOCK:
+		/*
+		 * There's no easy way to restart the syscall since other AIO's
+		 * may be already running. Just fail this IO with EINTR.
 		 */
-static ssize_t aio_run_iocb(struct kiocb *req, unsigned opcode,
-			    char __user *buf, size_t len, bool compat)
+		ret = -EINTR;
+		/*FALLTHRU*/
+	default:
+		aio_complete(req, ret, 0);
+		return 0;
+	}
+}
+
+static ssize_t aio_read(struct kiocb *req, struct iocb *iocb, bool vectored,
+		bool compat)
 {
 	struct file *file = req->ki_filp;
-	ssize_t ret;
-	int rw;
-	fmode_t mode;
-	rw_iter_op *iter_op;
 	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
 	struct iov_iter iter;
+	ssize_t ret;
 
-	switch (opcode) {
-	case IOCB_CMD_PREAD:
-	case IOCB_CMD_PREADV:
-		mode	= FMODE_READ;
-		rw	= READ;
-		iter_op	= file->f_op->read_iter;
-		goto rw_common;
-
-	case IOCB_CMD_PWRITE:
-	case IOCB_CMD_PWRITEV:
-		mode	= FMODE_WRITE;
-		rw	= WRITE;
-		iter_op	= file->f_op->write_iter;
-		goto rw_common;
-rw_common:
-		if (unlikely(!(file->f_mode & mode)))
+	if (unlikely(!(file->f_mode & FMODE_READ)))
 		return -EBADF;
-
-		if (!iter_op)
+	if (unlikely(!file->f_op->read_iter))
 		return -EINVAL;
 
-		if (opcode == IOCB_CMD_PREADV || opcode == IOCB_CMD_PWRITEV)
-			ret = aio_setup_vectored_rw(rw, buf, len,
-						&iovec, compat, &iter);
-		else {
-			ret = import_single_range(rw, buf, len, iovec, &iter);
-			iovec = NULL;
-		}
+	ret = aio_setup_rw(READ, iocb, &iovec, vectored, compat, &iter);
+	if (ret)
+		return ret;
+	ret = rw_verify_area(READ, file, &req->ki_pos, iov_iter_count(&iter));
 	if (!ret)
-			ret = rw_verify_area(rw, file, &req->ki_pos,
-					     iov_iter_count(&iter));
-		if (ret < 0) {
+		ret = aio_ret(req, file->f_op->read_iter(req, &iter));
 	kfree(iovec);
 	return ret;
-		}
-
-		get_file(file);
-		if (rw == WRITE)
-			file_start_write(file);
-
-		ret = iter_op(req, &iter);
+}
 
-		if (rw == WRITE)
-			file_end_write(file);
-		fput(file);
-		kfree(iovec);
-		break;
+static ssize_t aio_write(struct kiocb *req, struct iocb *iocb, bool vectored,
+		bool compat)
+{
+	struct file *file = req->ki_filp;
+	struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
+	struct iov_iter iter;
+	ssize_t ret;
 
-	default:
-		pr_debug("EINVAL: no operation provided\n");
+	if (unlikely(!(file->f_mode & FMODE_WRITE)))
+		return -EBADF;
+	if (unlikely(!file->f_op->write_iter))
 		return -EINVAL;
-	}
 
-	if (ret != -EIOCBQUEUED) {
-		/*
-		 * There's no easy way to restart the syscall since other AIO's
-		 * may be already running. Just fail this IO with EINTR.
-		 */
-		if (unlikely(ret == -ERESTARTSYS || ret == -ERESTARTNOINTR ||
-			     ret == -ERESTARTNOHAND ||
-			     ret == -ERESTART_RESTARTBLOCK))
-			ret = -EINTR;
-		aio_complete(req, ret, 0);
+	ret = aio_setup_rw(WRITE, iocb, &iovec, vectored, compat, &iter);
+	if (ret)
+		return ret;
+	ret = rw_verify_area(WRITE, file, &req->ki_pos, iov_iter_count(&iter));
+	if (!ret) {
+		file_start_write(file);
+		ret = aio_ret(req, file->f_op->write_iter(req, &iter));
+		file_end_write(file);
 	}
-
-	return 0;
+	kfree(iovec);
+	return ret;
 }
 
 static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
 			 struct iocb *iocb, bool compat)
 {
 	struct aio_kiocb *req;
+	struct file *file;
 	ssize_t ret;
 
 	/* enforce forwards compatibility on users */
@@ -1518,7 +1508,7 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
 	if (unlikely(!req))
 		return -EAGAIN;
 
-	req->common.ki_filp = fget(iocb->aio_fildes);
+	req->common.ki_filp = file = fget(iocb->aio_fildes);
 	if (unlikely(!req->common.ki_filp)) {
 		ret = -EBADF;
 		goto out_put_req;
@@ -1553,13 +1543,29 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
 	req->ki_user_iocb = user_iocb;
 	req->ki_user_data = iocb->aio_data;
 
-	ret = aio_run_iocb(&req->common, iocb->aio_lio_opcode,
-			   (char __user *)(unsigned long)iocb->aio_buf,
-			   iocb->aio_nbytes,
-			   compat);
-	if (ret)
-		goto out_put_req;
+	get_file(file);
+	switch (iocb->aio_lio_opcode) {
+	case IOCB_CMD_PREAD:
+		ret = aio_read(&req->common, iocb, false, compat);
+		break;
+	case IOCB_CMD_PWRITE:
+		ret = aio_write(&req->common, iocb, false, compat);
+		break;
+	case IOCB_CMD_PREADV:
+		ret = aio_read(&req->common, iocb, true, compat);
+		break;
+	case IOCB_CMD_PWRITEV:
+		ret = aio_write(&req->common, iocb, true, compat);
+		break;
+	default:
+		pr_debug("invalid aio operation %d\n", iocb->aio_lio_opcode);
+		ret = -EINVAL;
+		break;
+	}
+	fput(file);
 
+	if (ret && ret != -EIOCBQUEUED)
+		goto out_put_req;
 	return 0;
 out_put_req:
 	put_reqs_available(ctx, 1);