On Mon, 2016-05-02 at 07:56 -0700, Christoph Hellwig wrote:

quoted

index 79defba..97a1f5f 100644

--- a/fs/block_dev.c
+++ b/fs/block_dev.c

@@ -167,12 +167,21 @@ blkdev_direct_IO(struct kiocb *iocb, struct

iov_iter *iter, loff_t offset)
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = bdev_file_inode(file);
 
-	if (IS_DAX(inode))
+	if (iocb_is_direct(iocb))
+		return __blockdev_direct_IO(iocb, inode,
I_BDEV(inode), iter,
+					    offset,
blkdev_get_block, NULL,
+					    NULL,
DIO_SKIP_DIO_COUNT);
+	else if (iocb_is_dax(iocb))
 		return dax_do_io(iocb, inode, iter, offset,
blkdev_get_block,
 				NULL, DIO_SKIP_DIO_COUNT);
-	return __blockdev_direct_IO(iocb, inode, I_BDEV(inode),
iter, offset,
-				    blkdev_get_block, NULL, NULL,
-				    DIO_SKIP_DIO_COUNT);
+	else {
+		/*
+		 * If we're in the direct_IO path, either the
IOCB_DIRECT or
+		 * IOCB_DAX flags must be set.
+		 */
+		WARN_ONCE(1, "Kernel Bug with iocb flags\n");
+		return -ENXIO;
+	}

DAX should not even end up in ->direct_IO.

Do you mean to say remove the last 'else' clause entirely?
I agree that it should never be hit, which is why it is a WARN..
But I'm happy to remove it.

quoted

--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c

@@ -300,7 +300,7 @@ xfs_file_read_iter(

 
 	XFS_STATS_INC(mp, xs_read_calls);
 
-	if (unlikely(iocb->ki_flags & IOCB_DIRECT))
+	if (unlikely(iocb->ki_flags & (IOCB_DIRECT | IOCB_DAX)))
 		ioflags |= XFS_IO_ISDIRECT;

please also add a XFS_IO_ISDAX flag to propagate the information
properly and allow tracing to display the actual I/O type.

Will do.

quoted

+static inline bool iocb_is_dax(struct kiocb *iocb)
 {
+	return IS_DAX(file_inode(iocb->ki_filp)) &&
+		(iocb->ki_flags & IOCB_DAX);
+}
+
+static inline bool iocb_is_direct(struct kiocb *iocb)
+{
+	return iocb->ki_flags & IOCB_DIRECT;
 }

No need for these helpers - especially as IOCB_DAX should never be
set
if IS_DAX is false.

Ok. So check the flags directly where needed?

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