FAILED: patch "[PATCH] mm: cleancache: fix corruption on missed inode invalidation" failed to apply to 3.18-stable tree

The patch below does not apply to the 3.18-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: Pavel Tikhomirov <[email protected]>
Date: Fri, 30 Nov 2018 14:09:00 -0800
Subject: [PATCH] mm: cleancache: fix corruption on missed inode invalidation

If all pages are deleted from the mapping by memory reclaim and also moved to the cleancache:

__delete_from_page_cache
(no shadow case)
unaccount_page_cache_page
cleancache_put_page
page_cache_delete
mapping->nrpages -= nr
(nrpages becomes 0)

We don't clean the cleancache for an inode after final file truncation (removal).

truncate_inode_pages_final
check (nrpages || nrexceptional) is false
no truncate_inode_pages
no cleancache_invalidate_inode(mapping)

These way when reading the new file created with same inode we may get these trash leftover pages from cleancache and see wrong data instead of the contents of the new file.

Fix it by always doing truncate_inode_pages which is already ready for nrpages == 0 && nrexceptional == 0 case and just invalidates inode.

index 45d68e90b703..798e7ccfb030 100644
@@ -517,9 +517,13 @@ void truncate_inode_pages_final(struct address_space *mapping)
 		 */
 		xa_lock_irq(&mapping->i_pages);
 		xa_unlock_irq(&mapping->i_pages);
-
-		truncate_inode_pages(mapping, 0);
 	}
+
+	/*
+	 * Cleancache needs notification even if there are no pages or shadow
+	 * entries.
+	 */
+	truncate_inode_pages(mapping, 0);
 }
 EXPORT_SYMBOL(truncate_inode_pages_final);