fs: Remove unneeded IS_DAX() check in io_is_direct()

Remove the check because DAX now has it's own read/write methods and
file systems which support DAX check IS_DAX() prior to IOCB_DIRECT on
their own.  Therefore, it does not matter if the file state is DAX when
the iocb flags are created.

Also remove io_is_direct() as it is just a simple flag check.
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NIra Weiny <ira.weiny@intel.com>
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>

drivers/block/loop.c

@@ -634,8 +634,8 @@ static int do_req_filebacked(struct loop_device *lo, struct request *rq)
 
 static inline void loop_update_dio(struct loop_device *lo)
 {
-	__loop_update_dio(lo, io_is_direct(lo->lo_backing_file) |
-			lo->use_dio);
+	__loop_update_dio(lo, (lo->lo_backing_file->f_flags & O_DIRECT) |
+				lo->use_dio);
 }
 
 static void loop_reread_partitions(struct loop_device *lo,
@@ -1028,7 +1028,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode,
 	if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
 		blk_queue_write_cache(lo->lo_queue, true, false);
 
-	if (io_is_direct(lo->lo_backing_file) && inode->i_sb->s_bdev) {
+	if ((lo->lo_backing_file->f_flags & O_DIRECT) && inode->i_sb->s_bdev) {
 		/* In case of direct I/O, match underlying block size */
 		unsigned short bsize = bdev_logical_block_size(
 			inode->i_sb->s_bdev);

include/linux/fs.h

@@ -3394,11 +3394,6 @@ extern void setattr_copy(struct inode *inode, const struct iattr *attr);
 
 extern int file_update_time(struct file *file);
 
-static inline bool io_is_direct(struct file *filp)
-{
-	return (filp->f_flags & O_DIRECT) || IS_DAX(filp->f_mapping->host);
-}
-
 static inline bool vma_is_dax(const struct vm_area_struct *vma)
 {
 	return vma->vm_file && IS_DAX(vma->vm_file->f_mapping->host);
@@ -3423,7 +3418,7 @@ static inline int iocb_flags(struct file *file)
 	int res = 0;
 	if (file->f_flags & O_APPEND)
 		res |= IOCB_APPEND;
-	if (io_is_direct(file))
+	if (file->f_flags & O_DIRECT)
 		res |= IOCB_DIRECT;
 	if ((file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host))
 		res |= IOCB_DSYNC;