[PATCH] reserve space for swap label

Reserve space in the swap disk header for a LABEL and UUID to be specified.
 This has been possible with util-linux-2.12b (via e2fsprogs 1.36
libblkid), and is used by at least FC3 and later.  The kernel doesn't
really care about this, but the space shouldn't accidentally be used by
something else either.

Also make the on-disk structures be fixed-size types, instead of "int",
though I don't know of any architecture in use where an "int" isn't the
same size as a "__u32" (all current kernel arches have it as "unsigned
int").
Signed-off-by: Andreas Dilger <adilger@shaw.ca>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/swap.h

@@ -49,11 +49,13 @@ union swap_header {
 	} magic;
 	struct {
 		char		bootbits[1024];	/* Space for disklabel etc. */
-		unsigned int version;
-		unsigned int last_page;
-		unsigned int nr_badpages;
-		unsigned int padding[125];
-		unsigned int badpages[1];
+		__u32		version;
+		__u32		last_page;
+		__u32		nr_badpages;
+		unsigned char	sws_uuid[16];
+		unsigned char	sws_volume[16];
+		__u32		padding[117];
+		__u32		badpages[1];
 	} info;
 };