FAILED: patch "[PATCH] NFSv42: Fix pagecache invalidation after COPY/CLONE" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3f015d89a47cd8855cd92f71fff770095bd885a1 Mon Sep 17 00:00:00 2001
From: Benjamin Coddington <[email protected]>
Date: Tue, 16 Nov 2021 10:48:13 -0500
Subject: [PATCH] NFSv42: Fix pagecache invalidation after COPY/CLONE

The mechanism in use to allow the client to see the results of COPY/CLONE is to drop those pages from the pagecache. This forces the client to read those pages once more from the server. However, truncate_pagecache_range() zeros out partial pages instead of dropping them. Let us instead use invalidate_inode_pages2_range() with full-page offsets to ensure the client properly sees the results of COPY/CLONE operations.

index 08355b66e7cb..8b21ff1be717 100644
@@ -289,7 +289,9 @@ static void nfs42_copy_dest_done(struct inode *inode, loff_t pos, loff_t len)
 	loff_t newsize = pos + len;
 	loff_t end = newsize - 1;
 
-	truncate_pagecache_range(inode, pos, end);
+	WARN_ON_ONCE(invalidate_inode_pages2_range(inode->i_mapping,
+				pos >> PAGE_SHIFT, end >> PAGE_SHIFT));
+
 	spin_lock(&inode->i_lock);
 	if (newsize > i_size_read(inode))
 		i_size_write(inode, newsize);