[PATCH] Avoid !__GFP_IO allocations to eat from memory reservations

[Marcelo Tosatti]

Linus,

I just read pre3<->pre4 diff and it seems you missed this patch... here it
goes again.

In pre3/4, GFP_BUFFER allocations can eat from the "emergency" memory
reservations in case try_to_free_pages() fails for those allocations in
__alloc_pages().

Here goes the (tested) patch to fix that:

--- linux/mm/page_alloc.c.orig	Thu Jun 14 11:00:14 2001
+++ linux/mm/page_alloc.c	Thu Jun 14 11:32:56 2001
@@ -453,6 +453,12 @@
 				int progress = try_to_free_pages(gfp_mask);
 				if (progress || gfp_mask & __GFP_IO)
 					goto try_again;
+				/*
+				 * Fail in case no progress was made and the
+				 * allocation may not be able to block on IO.
+				 */
+				else
+					return NULL;
 			}
 		}
 	}