ovl: use simpler function to convert iocb to rw flags

Overlayfs implements its own function to translate iocb flags into rw
flags, so that they can be passed into another vfs call.

With commit ce71bfea ("fs: align IOCB_* flags with RWF_* flags")
Jens created a 1:1 matching between the iocb flags and rw flags,
simplifying the conversion.
Signed-off-by: Alessio Balsini <balsini@android.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

fs/overlayfs/file.c

@@ -263,20 +263,12 @@ static void ovl_file_accessed(struct file *file)
 	touch_atime(&file->f_path);
 }
 
-static rwf_t ovl_iocb_to_rwf(int ifl)
+#define OVL_IOCB_MASK \
+	(IOCB_NOWAIT | IOCB_HIPRI | IOCB_DSYNC | IOCB_SYNC)
+
+static rwf_t iocb_to_rw_flags(int flags)
 {
-	rwf_t flags = 0;
-
-	if (ifl & IOCB_NOWAIT)
-		flags |= RWF_NOWAIT;
-	if (ifl & IOCB_HIPRI)
-		flags |= RWF_HIPRI;
-	if (ifl & IOCB_DSYNC)
-		flags |= RWF_DSYNC;
-	if (ifl & IOCB_SYNC)
-		flags |= RWF_SYNC;
-
-	return flags;
+	return (__force rwf_t)(flags & OVL_IOCB_MASK);
 }
 
 static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
@@ -334,8 +326,9 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	if (is_sync_kiocb(iocb)) {
-		ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
-				    ovl_iocb_to_rwf(iocb->ki_flags));
+		rwf_t rwf = iocb_to_rw_flags(iocb->ki_flags);
+
+		ret = vfs_iter_read(real.file, iter, &iocb->ki_pos, rwf);
 	} else {
 		struct ovl_aio_req *aio_req;
 
@@ -401,9 +394,10 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 
 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	if (is_sync_kiocb(iocb)) {
+		rwf_t rwf = iocb_to_rw_flags(ifl);
+
 		file_start_write(real.file);
-		ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
-				     ovl_iocb_to_rwf(ifl));
+		ret = vfs_iter_write(real.file, iter, &iocb->ki_pos, rwf);
 		file_end_write(real.file);
 		/* Update size */
 		ovl_copyattr(inode);