staging: kpc2000: kpc_dma: Convert set_page_dirty() --> set_page_dirty_lock()

First, convert set_page_dirty() to set_page_dirty_lock()

Second, there is an interval in there after set_page_dirty() and
before put_page(), in which the device could be running and setting
pages dirty. Moving set_page_dirty_lock() after dma_unmap_sg().
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Suggested-by: John Hubbard <jhubbard@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Bharath Vedartham <linux.bhar@gmail.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/1593584264-16982-3-git-send-email-jrdr.linux@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/kpc2000/kpc_dma/fileops.c

@@ -215,13 +215,13 @@ void  transfer_complete_cb(struct aio_cb_data *acd, size_t xfr_count, u32 flags)
 	BUG_ON(!acd->ldev);
 	BUG_ON(!acd->ldev->pldev);
 
+	dma_unmap_sg(&acd->ldev->pldev->dev, acd->sgt.sgl, acd->sgt.nents, acd->ldev->dir);
+
 	for (i = 0 ; i < acd->page_count ; i++) {
 		if (!PageReserved(acd->user_pages[i]))
-			set_page_dirty(acd->user_pages[i]);
+			set_page_dirty_lock(acd->user_pages[i]);
 	}
 
-	dma_unmap_sg(&acd->ldev->pldev->dev, acd->sgt.sgl, acd->sgt.nents, acd->ldev->dir);
-
 	for (i = 0 ; i < acd->page_count ; i++)
 		put_page(acd->user_pages[i]);