direct_IO: use iov_iter_rw() instead of rw everywhere

The rw parameter to direct_IO is redundant with iov_iter->type, and
treated slightly differently just about everywhere it's used: some users
do rw & WRITE, and others do rw == WRITE where they should be doing a
bitwise check. Simplify this with the new iov_iter_rw() helper, which
always returns either READ or WRITE.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ext4/indirect.c

@@ -642,8 +642,8 @@ out:
  * crashes then stale disk data _may_ be exposed inside the file. But current
  * VFS code falls back into buffered path in that case so we are safe.
  */
-ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
-			   struct iov_iter *iter, loff_t offset)
+ssize_t ext4_ind_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
+			   loff_t offset)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
@@ -654,7 +654,7 @@ ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
 	size_t count = iov_iter_count(iter);
 	int retries = 0;
 
-	if (rw == WRITE) {
+	if (iov_iter_rw(iter) == WRITE) {
 		loff_t final_size = offset + count;
 
 		if (final_size > inode->i_size) {
@@ -676,7 +676,7 @@ ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
 	}
 
 retry:
-	if (rw == READ && ext4_should_dioread_nolock(inode)) {
+	if (iov_iter_rw(iter) == READ && ext4_should_dioread_nolock(inode)) {
 		/*
 		 * Nolock dioread optimization may be dynamically disabled
 		 * via ext4_inode_block_unlocked_dio(). Check inode's state
@@ -707,7 +707,7 @@ locked:
 			ret = blockdev_direct_IO(iocb, inode, iter, offset,
 						 ext4_get_block);
 
-		if (unlikely((rw & WRITE) && ret < 0)) {
+		if (unlikely(iov_iter_rw(iter) == WRITE && ret < 0)) {
 			loff_t isize = i_size_read(inode);
 			loff_t end = offset + count;