NFSv42: Fix pagecache invalidation after COPY/CLONE

commit 3f015d8 upstream.

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.

Cc: <stable@vger.kernel.org> # v4.7+
Fixes: 2e72448 ("NFS: Add COPY nfs operation")
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/nfs/nfs42proc.c

@@ -362,8 +362,9 @@ static ssize_t _nfs42_proc_copy(struct file *src,
 			goto out;
 	}
 
-	truncate_pagecache_range(dst_inode, pos_dst,
-				 pos_dst + res->write_res.count);
+	WARN_ON_ONCE(invalidate_inode_pages2_range(dst_inode->i_mapping,
+					pos_dst >> PAGE_SHIFT,
+					(pos_dst + res->write_res.count - 1) >> PAGE_SHIFT));
 	spin_lock(&dst_inode->i_lock);
 	NFS_I(dst_inode)->cache_validity |= (NFS_INO_REVAL_PAGECACHE |
 			NFS_INO_REVAL_FORCED | NFS_INO_INVALID_SIZE |