On Tue, Apr 28, 2009 at 06:11:06PM -0400, Chuck Lever wrote: > This patch is simply a clean up. We don't need to use put_unaligned in > nsm_init_private. There is absolutely nothing special about the > nsm_private data type that would require this. It should be accessed > and modified the way all other RPC opaques are, via memset/memcpy. > > Take a look at http://thread.gmane.org/gmane.linux.nfs/25607 and commit > ad5b365c. > > The controversy is over how to define opaques so they are accessible on > both 32- and 64-bit hardware platforms. My first pass at > nsm_init_private worked on 32-bit systems, but broke on 64-bit systems. > An expedient fix for this was to add the put_unaligned in there so 64-bit > systems could access the field no matter how it was aligned. I argue > this is unneeded complexity, and inconsistent with the way most other RPC > opaques are treated in the kernel. > > Andrew Morton proposed making RPC opaques a union of u8, u32 (or > __be32), and u64 -- the u8 would allow us to treat an opaque as a byte > array when needed, the u32 would allow access via XDR quads, and the u64 > would force 64-bit alignment. The issues with this are: > > 1. Defined this way, opaque fields in data structures will force the > encompassing structures to be large enough to honor the alignment > requirements of the fields, and > > 2. Most other RPC opaques are already defined as character arrays, so > we would have to visit all of them to see if there were issues. > > If we insist on accessing opaques only via memset() and memcpy() problem > 1 goes away and we remain compatible with the traditional definition of > an RPC opaque as an array of bytes, on both 64- and 32-bit systems. > > The description for this patch can be rewritten this way: > > "Clean up: There is nothing special about the nsm_private data type that > requires the use of put_unaligned() to access it. Rewrite > nsm_init_private so it accesses nsm_private the way other code accesses > other RPC opaques. > > See kernel bugzilla 12995." OK.--b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
