[PATCH] zoned vm counters: conversion of nr_dirty to per zone counter

This makes nr_dirty a per zone counter.  Looping over all processors is
avoided during writeback state determination.

The counter aggregation for nr_dirty had to be undone in the NFS layer since
we summed up the page counts from multiple zones.  Someone more familiar with
NFS should probably review what I have done.

[akpm@osdl.org: bugfix]
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 031b27a..e5ad107 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -464,7 +464,7 @@
 		.range_start	= 0,
 		.range_end	= LLONG_MAX,
 	};
-	unsigned long nr_dirty = read_page_state(nr_dirty);
+	unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
 	unsigned long nr_unstable = read_page_state(nr_unstable);
 
 	wbc.nr_to_write = nr_dirty + nr_unstable +