[PATCH] mm: call into direct reclaim without PF_MEMALLOC set

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

(Sorry about the dup Andrew, I noticed I hit the wrong reply button)

OK, so how about this?

No use running direct reclaim if we're already in there.

---

PF_MEMALLOC is also used to prevent recursion of direct reclaim.
However this invocation does not set PF_MEMALLOC nor checks it and
hence a can make it nest a single time. Either by reaching this
spot from reclaim and then calling it again or entering here and 
encountering a __GFP_WAIT alloc from within.

So check for PF_MEMALLOC and avoid a second invocation and otherwise
set PF_MEMALLOC.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 fs/buffer.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

Index: linux-2.6-git/fs/buffer.c
===================================================================
--- linux-2.6-git.orig/fs/buffer.c	2006-11-15 20:32:14.000000000 +0100
+++ linux-2.6-git/fs/buffer.c	2006-11-15 21:52:05.000000000 +0100
@@ -360,8 +360,18 @@ static void free_more_memory(void)
 
 	for_each_online_pgdat(pgdat) {
 		zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones;
-		if (*zones)
+		if (*zones && !(current->flags & PF_MEMALLOC)) {
+			struct task_struct *p = current;
+			struct reclaim_state reclaim_state = { 0 };
+
+			p->flags |= PF_MEMALLOC;
+			p->reclaim_state = &reclaim_state;
+
 			try_to_free_pages(zones, GFP_NOFS);
+
+			p->reclaim_state = NULL;
+			p->flags &= ~PF_MEMALLOC;
+		}
 	}
 }
 


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