Re: [PATCH] shrink_list: Use of && instead || leads to unintended writing of pages

[Christoph Lameter <clameter@engr.sgi.com>]

This is all crap. may_writepage needs to do as it says and control 
write behavior .... We can set the  proper writemode in try_to_free_pages 
based on the laptop mode. Then everything falls into the proper place.



[PATCH] Implement sane function of sc->may_writepage

Make sc->may_writepage control the writeout behavior of shrink_list.

Remove the laptop_mode trick from shrink_list and instead set may_writepage in
try_to_free_pages properly.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.16-rc1-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.16-rc1-mm1.orig/mm/vmscan.c	2006-01-19 15:50:19.000000000 -0800
+++ linux-2.6.16-rc1-mm1/mm/vmscan.c	2006-01-19 17:42:07.000000000 -0800
@@ -491,7 +491,7 @@ static int shrink_list(struct list_head 
 				goto keep_locked;
 			if (!may_enter_fs)
 				goto keep_locked;
-			if (laptop_mode && !sc->may_writepage)
+			if (!sc->may_writepage)
 				goto keep_locked;
 
 			/* Page is dirty, try to write it out here */
@@ -1409,7 +1409,7 @@ int try_to_free_pages(struct zone **zone
 	int i;
 
 	sc.gfp_mask = gfp_mask;
-	sc.may_writepage = 0;
+	sc.may_writepage = !laptop_mode;
 	sc.may_swap = 1;
 
 	inc_page_state(allocstall);
@@ -1512,7 +1512,7 @@ loop_again:
 	total_scanned = 0;
 	total_reclaimed = 0;
 	sc.gfp_mask = GFP_KERNEL;
-	sc.may_writepage = 0;
+	sc.may_writepage = 1;
 	sc.may_swap = 1;
 	sc.nr_mapped = read_page_state(nr_mapped);
 
-
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