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

[Christoph Lameter]

On Thu, 19 Jan 2006, Andrew Morton wrote:

> laptop_mode=1: don't write out dirty pages if we're only performing light
> scanning.  But do write them out once page reclaim starts getting into
> difficulty.

Ahh. Now I see ..... Wrong field.

> I guess if zone reclaim wants to permanently disable writeback then it'll
> be needing a new scan_control flag for that.  Which means that we need to

We have such a flag and its called may_swap (was introduced by Martin 
Hicks). If we cannot swap then we should not write out pages.

Thus we need this fix instead:

Signed-off-by: Christoph Lameter <clameter@xxxxxxx>

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 17:26:50.000000000 -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 ((laptop_mode && !sc->may_writepage) || !sc->may_swap)
 				goto keep_locked;
 
 			/* Page is dirty, try to write it out here */
-
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