From: David Howells<dhowells@redhat.com>
Subject: [RHEL5/FC6 PATCH] CacheFiles: cachefiles_write_page() shouldn't indicate error twice
Date: Wed, 30 Aug 2006 12:45:49
Bugzilla: 204570
Message-Id: <988.1156956349@warthog.cambridge.redhat.com>
Changelog: CacheFiles: cachefiles_write_page() shouldn't indicate error twice


Prevent cachefiles_write_page() from issuing an error twice, instead forgoing
the callback if it can return the error directly [BZ 204570].

Previously, the netfs was being informed of the error twice, once by the error
being passed to the netfs callback, and a second time when fscache_write_page()
returned to the netfs.

In NFS's case, this meant it attempted to do error handling twice, including
clearing PG_fs_misc twice...

I've reproduced this and tested it on my testbox using a vanilla kernel.  Steve
Dickson has also tested it.

David Howells
---

 fs/cachefiles/cf-interface.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

Index: latest/fs/cachefiles/cf-interface.c
===================================================================
--- latest.orig/fs/cachefiles/cf-interface.c
+++ latest/fs/cachefiles/cf-interface.c
@@ -1265,9 +1265,11 @@ static int cachefiles_write_page(struct 
 						"write page to backing file"
 						" failed");
 		ret = -ENOBUFS;
+	} else {
+		/* only invoke the callback if successful, we return the error
+		 * directly otherwise */
+		end_io_func(page, context, ret);
 	}
-
-	end_io_func(page, context, ret);
 #endif
 
 	_leave(" = %d", ret);