SetPageDirty() and ClearPageDirty() are low-level thing which filesystems
shouldn't be using.  They bypass dirty page accounting.

Cc: David Woodhouse <dwmw2@infradead.org>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>