[PATCH] mm: don't set __GFP_WRITE on ramfs/sysfs writes

[Fengguang Wu <fengguang.wu@intel.com>]

There is not much of a point in skipping zones during allocation based
on the dirty usage which they'll never contribute to. And we'd like to
avoid page reclaim waits when writing to ramfs/sysfs etc.

Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
---
 mm/filemap.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- linux.orig/mm/filemap.c	2012-03-02 14:06:47.000000000 +0800
+++ linux/mm/filemap.c	2012-03-02 14:07:21.325766507 +0800
@@ -2341,7 +2341,9 @@ struct page *grab_cache_page_write_begin
 	struct page *page;
 	gfp_t gfp_notmask = 0;
 
-	gfp_mask = mapping_gfp_mask(mapping) | __GFP_WRITE;
+	gfp_mask = mapping_gfp_mask(mapping);
+	if (mapping_cap_account_dirty(mapping))
+		gfp_mask |= __GFP_WRITE;
 	if (flags & AOP_FLAG_NOFS)
 		gfp_notmask = __GFP_FS;
 repeat:

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