Sing the praises of `gcc -W'.  Would have prevented that blockdev direct-IO
bug.

Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>